On the Structure of a Earthworn m allie tod Nemertodrilus ...These are the only apertures belonging to the genital system which are paired. The male genital pore is unpaired and median;

STBUOTURE OF EARTHWORM ALLIED TO NEMERTODRILTJS. 539

On the Structure of an Earthworm allied toNemertodrilus, Mich., with Observationson the Post - embryonic Development ofCertain Organs.

By

Frank. E. Beddard, M.A.,Prosector of the Zoological Society of London, Lecturer on Biology at

Guy's Hospital.

With Plates XXXVIII and XXXIX.

TABLE OP CONTENTS.

I. Introductory, p. 539.II . List of Memoirs consulted, p.

541.

III. External Characters, p. 542.

IV. Anatomy and Histology, p. 544.

V. Description of some YoungStages, p. 572.

VI. Homologies of the Reproduc-tive Organs in Eudrilidse, p.579.

VII. Definition of Genus Libyo-drilus and Species L. vio-laceus, p. 583.

VIII. Summary, p. 583.IX. Explanation of Plates, p. 585.

I. Introductory.THE investigations of Rosa (5),1 Michaelsen (3, 4), and more

recently of myself (1), have shown that the earthworm fauna oftropical Africa is characterised by an extraordinary abundanceand diversity of types of the family Eudrilidse. This familyhad been known for along time by the genus Eudr i lu s alone,which seemed to occupy—principally on account of the struc-ture of the reproductive system—a somewhat isolated positionamong the Oligochasta.

1 The numbers in brackets refer to the list of papers on p. 541.

540 FEANK E. BBDDABD.

Eudr i lus itself has been only lately received from theAfrican continent; but no leBs than eight new genera of thisfamily have been within the last year recorded from thence.I have myself on two separate occasions received worms fromLagos, which proved to be the types of three new genera;this shows the great abundance of forms which must remainto be discovered.

In a recent number of this Journal (1) I described twogenera—Hyperiodrilus and Heliodrilus—which I ob-tained from the Royal Gardens at Kew; they were found inearth which had come from Lagos. In all probability thegenus S iphonogas te r , of which I have given a brief noticein the last published number of the ' Proceedings of the Zoo-logical Society/ will prove to be a Eudrilid; this worm wasdiscovered by Mr. Alvan Millson, Assistant Colonial Secretaryat Lagos, who has contributed to the 'Kew Bulletin' ofOctober, 1890, a very interesting account of its habits. Thesame gentleman was so good as to bring over with him a largeboK full of living earthworms from Lagos, which includedsome specimens of the "Yoruba worm;" unfortunately theselatter disappeared during the voyage, but the other speciessurvived ; it proves to be the type of a perfectly distinct andnew genus, which presents some remarkable peculiarities ofstructure. In the box were also some examples of a small worm,which appears to be an Al lo lobophora , and some very youngexamples of the new Eudrilid. The opportunity thus affordedme of contributing something towards the development of thereproductive system andnephridia of L ibyodr i lus violaceuscauses me to feel less regret that it was impossible to keep thespecies alive in order that they might breed.

I am greatly indebted to Mr. Alvan Millson for hiskindness.

STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRIMJS. 541

II. List of Memoirs consulted.

(1) BEDDASD, F. E.—'• On the Structure of Two New Genera of Eudrilidea,with Remarks on Nemertodrilus, Mich.," 'Quart. Journ. Micr.Sci.,' March, 1891.

(2) BEDDARD, F. E.—" On the Occurrence of Numerous Nephridia in thesame Segment in Certain Earthworms, and on the Relationship betweenthe Excretory System in the Annelides and in the Platyhelminths,"'Quart. Journ. Mior. Sci.,' vol. xxviii, N. S., p. 397.

(3) MICHAELSEN, W.—" Beschreibung der von Herrn Dr. Franz Stuhlmannim Mundungsgebiet des Sambesi gesammelten Terricolen," 'Jahrb.Hamb. Wiss. Anat.,' Bd. vii.

(4) MICHAELSEN, W.—" Oligochaeten des Naturhistorisclien Museums inHamburg," iv; ibid., Bd. viii.

(5) ROSA, D.—" Lombriohi dello Scioa," 'Ann. Mus. Civ. Genova,' 1888.(6) HORST, R.—" Note on a New Earthworm," ' Zool. Anz.,' 1891.(7) HOEST, R.—" Sur quelques Lombriciens exotiquea appartenant au genre

Eudrilus," ' Mdm. Soe. Zool.,' 1890, p. 223.(8) CERPONTAINE, P.—" Recherches sur le Systeme Cutan6 et sur le Systeme

Musculaire du Lombric Terrestre (Lumbricus agricola, Hoffmcis-ter)," ' M<§m. cour. et Mem. sav. e"tr. Acad. Roy. Belg.,' 1890. (Thispaper is reprinted in ' Arch, de Biol.')

(9) SPENCER, W. B.—"The Anatomy of Megascolides australis (theGiant Earthworm of Gippsland)," 'Trans. Roy. Soc. Victoria,' vol. i,part 1.

(10) PERRIER, E.—" Me'moires pour servir a l'histoire des Lombriciensterrestres," ' Nouv. Arch. Mus.,' t. viii.

(11) BENHAM, W. B.—" Atrium or Prostate P" ' Zool. Anz.,' 1890.(12) D'UDEKEM, J.—"Histoire Naturelle du Tubifex des Ruisseaux,"

1 Mem. cour. et M6m. des sav. etr.,' 1853.(13) HORSI, R.—" Descriptions of Earthworms," I, ' Notes Leyden Mus.,'

vol. ix, p. 97.(14) EISIG, H.—" Die Capitelliden," in ' Fauna and Flora des Golfes von

Neapel.'(15) BEDDARD, F. E.—" Contributions to the Anatomy of Earthworms,"

No. I, ' Proc. Zool. Soc.,' 1887.

542 FRANK B. BEDDARD.

III. External Characters.

The worms were brought over in a large wooden [box nearlyfilled with a sandy loam; they preferred the bottom of thebox, and were in nearly every case found in close contact withthe wood; this may be perhaps owing to the greater warmth.The worms were very inactive in their movements; but this ispossibly not so much a characteristic of the species as due tothe coldness of the weather. Nevertheless I have not found thattropical Perichseta, which are the most agile of earthworms,are in any way influenced by such causes.

The colour of the species is a dull purplish brown with adistinct pinkish tinge; the clitellum is only to be distinguishedby its darker colour. The colouring substance was largelydissolved out by alcohol staining the fluid of a greenish yellow.There remained, however, after treatment with alcohol, a darkcoloration on the dorsal surface.

The worms, when placed in spirit, protruded the buccalcavity, which appeared of a bright red colour; they do notprotrude it in locomotion, as Perichseta does.

Pros to mi urn.—The prostomiumis short, and not continuedby a groove on to the buccal segment.

Setae.—The setae are strictly paired, and lie upon the ventralsurface of the animal. There is nothing unusual in theirform. The ventral setge of Segment 17 are absent, as shownin the illustration (fig. 2). The lateral and ventral setae of eachside of the body are connected by a muscular slip shown infig. 19, M.

Dorsa l pores appear to be, as in other Eudrilids, entirelyabsent.

Nephr id iopores , usually conspicuous enough in thisfamily, could not be detected in the present species (see, how-ever, p. 556) even with a lens.

The c l i t e l lum is continuously developed all round thebody : in most specimens it occupied only two segments, vizNos. 15 and 16; in some, however, it extended over the 14th

STRUCTURE OF EARTHWORM ALLIED TO NBMBRTODRILUS. 543

also. The extent of the clitellum is more limited than inother Eudrilids, where four to six segments appear to be therule.

Spermathecal Pore.—This is situated in the middleventral line (see fig. 2, sp) of Segment 13; it lies betweenthe ventral pairs of setae; the aperture itself is small, butits position is rendered somewhat conspicuous by beingplaced upon the summit of a slight swelling of a yellowishcolour.

Oviducal Pores.—These pores occupy what is, at present,an unique position among earthworms. With the exceptionof certain species of Moniligaster, and with the possibleexception of Eisenia (= Tetragonurus of Eisen), the ovi-ducts of earthworms appear to open invariably upon the 14thsegment. In the present species they are situated on Seg-ment 15. I took particular pains to assure myself that thiswas really the case; in half a dozen or so of individuals whichwere marked by having these orifices very conspicuous theywere certainly situated on that segment. The oviducal poresin this worm are not difficult to see; indeed, these aperturesare for the most part particularly plain in the Eudrilidse. Thisis due to the fact that the end of the oviduct is often slightlyprotruded, and forms a round whitish elevation contrasting incolour with the surrounding dark integument. I mentionthese facts more particularly for the purpose of showing thatI am not likely to have fallen into an error in assigning thisabnormal position to the oviduct pore. The pore in Libyo-drilus has the same appearance as I have figured anddescribed in Heliodrilus (1); that is to say, it is a whitishknob upon the segment: it lies to the outside of and alittle in front of the lateral pair of setae, but well behind thegroove which separates its segment (the 15th) from the 14th.These are the only apertures belonging to the genital systemwhich are paired.

The male genital pore is unpaired and median; it lies onthe border line of Segments 17, 18. The aperture lies uponthe summit of a conspicuous elevation of the integument; the

544 FRANK B. BEDDABD.

two penial setae may be often seen protruding from theorifice.

I found no gen i ta l papillae of any kind.

IV. Anatomy and Histology.

§ Body-wal l .

Epidermis.—The chief point to be noted about the epi-dermis is the absence of the peculiar sense organs so generallyfound among the Eudrilidae. I have described them inEudr i lus , Hype r iod r i l u s , and Hel iodr i lus . Dr. Horsthas recently described them in an African species of Eud r i l u s ,and was the first to suggest that they were possibly senseorgans; he compares them to the Pacinian bodies of Verte-brata. I had originally considered these bodies as repre-senting rudimentary setae, and as corresponding to thoseepidermal structures in Urochseta which Perrier first de-scribed, and considered as rudimentary setae; but a moredetailed examination of their structure led me to express inmy paper upon H y p e r i o d r i l u s and H e l i o d r i l u s anopinion that they were of a sensory nature, and to make theidentical comparison that Dr. Horst made, previously in pointof time of publication. Rosa has found these structures inT e l e u d r i l u s ; but they do not exist in N e m e r t o d r i l u s orin L ibyodr i lu s . The absence of these epidermal senseorgans unites these two genera, which have other points incommon.

The cells of the epidermis are of the usual kind; the largeglandular cells appear to be perhaps unusually abundant. Ihave not made a special study of the histology of the epi-dermis, which has been recently so elaborately worked outand so beautifully illustrated in L u m b r i c u s b y M . Cerfon-taine (8).

M u s c u l a r Layers.—The usual circular and longitudinalmuscles are present; the relative thickness of the two coatsmay be judged from figs. 4 and 13. In. both layers the fibres

STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRILTJS. 545

are embedded in a gelatinous-looking matrix, which is moreabundant in proportion to the muscular tissue in the case ofthe longitudinal coat. As to the fibres themselves, I find that,as M. Cerfontaine has described in Lumbricus (8), both,those of the longitudinal and circular coat present a radiatelystriate appearance, the striae converging towards a centralclear space. I have not taken any special means to investi-gate thoroughly the histological structure of the muscles, Ionly describe what I have seen in transverse and longitudinalsections of the entire worm; but I have little doubt from whatI have been able to see that the results of M. Cerfontaine'sinvestigations into Lumbricus will hold for Libyodrilusalso. The matrix in which the fibres are embedded can hardlybe termed granular in Libyodrilus; it has a gelatinoushomogeneous appearance, and is but slightly affected by boraxcarmine. It forms a specially thick layer (fig. 14) betweenthe end of the longitudinal muscular fibres and the perito-neum. The fibres—both those of the circular and the longi-tudinal coat—tend to be grouped into definite areas, whichare only separated from each other by the thickness of thematrix lying between them. I quite agree {with M. Cerfon-taine that there is nothing comparable to the septa describedby Claparede. No doubt such an appearance might be pro-duced by great shrinking, caused by preservation in strongalcohol without previously fixing the tissues.

The arrangement of the fibres of both muscular coats isregular, but the regularity is not so great as in certain speciesof Lumbricus and Allolobophora ; each " compartment"is made up of fibres, which are three, four, or five deep—evenmore sometimes.

It is an interesting fact that in the young worm the fibresare disposed much more nearly in the bipinnate fashion origi-nally made known by the descriptions of Clapare'de.

§ Ccelom and Intersegmental Septa.The first septum separates Segments 4—5; in front of

this the pharynx is attached to the parietes by numerous muscu-VOL. XXXII, PART IY. NEW SEB. 0 0

546 FRANK E. BEDDARD.

lar bands which occupy a good deal of the coelomic space: itis probable that the reduction of the nephridia in this regionof the body is brought about by the development of this exten-sive meshwork of muscles. The septa which lie behind thefirst are thickened, and formed often of distinct layers of fibres.The last of the thick septa separates Segments 11—12;the next septum, however (see fig. 1), although not sothick as those which precede it, is thicker than those whichfollow.

A noteworthy point is the non-coincidence of the insertionof the septa with the intersegmental furrows. This frequentlyoccurs in earthworms, but according to Rosa it is possible totrace the fibres belonging to the septum from their apparentattachment to the middle of the segment to their real insertioninto the intersegmental furrow. I could not trace any sucharrangement in L ibyodr i l u s . The first septum which has anabnormal insertion is 12—13; this and the following six orseven are attached near to the middle of the segment just infront of the setae. It is only dorsally and laterally that thesepta are so attached; ventrally their insertion is quite regular.I have mentioned on page 571 the effect produced upon theposition of the oviducal pore by the shifting of the interseg-mental septum 14—15.

The principal point of interest in connection with the coelomis the separation of spaces which surround some of the organs.In my description of the vascular system I have referred to theperihsemal space which encloses the subcEsophageal blood-vessels ; besides this space, the areas surrounding both of thelateral pair of setse are enclosed by a membrane shutting themoff from the general body-cavity of their segments. A seriesof transverse sections, such as the one illustrated in fig. 19,shows that this membrane is perfectly continuous everywhere,forming a distinct chamber, which is prolonged round the setasac and nearly reaches the circular muscular coat. In theCapitellidse Eisig has described somewhat similar lateralchambers, into the floors of which the setse are inserted; but Iam not aware that anything of the kind has until now been

STRUCTURE OP EARTHWORM ALLIED TO NEMERTODRILUS. 547

described in the Oligochseta. As will be seen from fig. 19,the muscle connecting the two pair3 of setae lies within thechamber. The membrane which forms the walls of thechamber is nearly homogeneous in appearance, with a coveringand lining of epithelium only recognisable by the nuclei.

§ A l i m e n t a r y Canal.

The alimentary canal of L i b y o d r i l u s presents certain im-portant differences from that of other Eudrilidse. There is inthe first place no trace that I could discover of oesophagealglands, or of those impaired ventral pouches termed " chylus-taschen" by Michaelsen, which occur in so many Eudrilids.

The position of the three gizzards is another point of interest.In He l iodr i lus and H y p e r i o d r i l u s there are a largernumber of gizzards, which are situated as in L u m b r i c u s atthe junction of the oesophagus and intestine j the three gizzardsof L ibyodr i l u s occupy a similar position.

In his memoir upon the classification of earthworms Perrierremarked upon the occurrence in all the Anticlitellians of thegizzard behind the organs of generation and the contractilehearts of the vascular system ; from this group he distinguishedboth the Post- and Intra-clitellian worms by the fact that thegizzard was placed in front of the essential organs of repro-duction.

This distinction held good until my own discovery ofthe position of the gizzards in the two Eudrilids abovereferred to. In some forms—for instance, a Teleudri lus—thegizzard has the forward position which characterises themajority of worms belonging to Perrier's two groups of Intra-clitellians and Postclitellians j but I am disposed to thinkthat the arrangement of these organs found in He l iod r i lu s ,Hype r iod r i l u s , and L ibyodr i l u s will prove to be morecharacteristic of the group. There are no particular reasonsthat I can see for placing the Eudrilidae in the neighbourhoodof the Lumbricidae, and thus one of the characters of the lattergroup can no longer be regarded as distinctive. Dr. Horst


has already shown in his brief account (6) of an evidently veryinteresting form, G l y p h i d r i l u s Weber i , that the position ofthe clitellum hitherto found only among the Lumbricidae isalso to be found in a worm clearly referable to Perrier'sIntraclitellians. The varying position of the gizzard is lessremarkable now that there is some probability of its epithe-lium being always derived from the hypoblast; if the olderview that the gizzard belonged to the stomodseal invaginationhad been confirmed by more recent researches, it would havebeen necessary to regard the calciferous pouches as beingepiblastic when in front of the gizzard and hypoblastic whenlying behind it. The relations of the same diverticula show thatwhen the gizzard is followed immediately by the " large in-testine " it does not mean that there has been a suppression ofthe small intestine immediately following the gizzard. Theabsence of any relation between the position of the gizzard (orgizzards) and the position of other organs seems to show clearlythat this modification of the walls of the anterior section ofthe gut may take place anywhere. There is no need to assumethat the gizzard of one earthworm is the exact homologue ofthat of another.

The pha rynx occupies the first five segments.The oesophagus is of great length, and divided into two

distinct sections, neither of which, as already mentioned, isfurnished with glandular diverticula. The first section of thetube is of narrower calibre, and extends as far as the end ofSegment 19. After this the tube becomes suddenly dilated andforms a kind of crop, which immediately precedes the gizzards.The " crop " occupies Segments 20—22 inclusive.

As to histological structure, the oesophagus does not differfrom that of other earthworms; its walls are exceedinglyvascular, and the epithelium is in many parts rather thin.Even in the 12th segment there are a few chloragogen cellsupon the oesophagus. These become largely developed in Seg-ment 15, where the oesophagus is as closely enveloped by themas is the intestine; the transition, however, appears to begradual. Thelatter part of the oesophagus from about Segment

STRUCTURE OF EARTHWORM ALLIED TO NEMERTODRILUS. 549

14 onwards is ciliated; its epithelium is thrown into regularlongitudinal folds ; the cells are tall and columnar, and themuscular coat is of an appreciable thickness.

The oesophagus is extremely vascular ; in longitudinal andtransverse sections its walls have from this cause a moniliformappearance (fig. 16). So far as I could make out, the plexus ofblood-vessels which lies immediately below the epidermis wasnowhere a sinus, although the individual vessels were so closetogether as to give this appearance; still a more carefulexamination showed the longitudinally running connectingbranches between the much wider circular vessels.

The th ree gizzards are in Segments 23, 24, and 25—onegizzard to each segment; they are not all three directly con-tinuous, but are separated by a certain amount of soft-walled in-testine. The soft-walled portion occupies the anterior part ofeach gizzard segment; posteriorly, the gizzard comes into con-tact with the septum.

The width of the crop gives the gizzards the appearance ofbeing strung, as it were, upon the intestine; but that thecrop belongs to the oesophagus and not to the intestine is shownby the fact that it has no typhlosole.

The in tes t ine is furnished with a typhlosole which is of asomewhat unusual form. From its very commencement to asfar back as Segment 37, three folds can be seen on a dissection—one median, and one on each side. The median fold corre-sponds, of course, to the dorsal vessel, and is of about thrice thevertical diameter of each of the two lateral folds. All threefolds were quite conspicuous in dissections from their redcolour. After the 37th segment the two lateral folds disap-peared, but the median typhlosole continued on to near theend of the body.

In dissected worms, both fresh and after preservation, theintestine was of a rich mahogany brown colour, quite differentfrom the colour of our British L u m b r i c i ; N e m e r t o d r i l u sand some of the other Eudrilids agree with the present species inthis particular, which is due to the abundance and darkness ofthe granules in the chloragogen cells.


§ Ci rcu la to ry System and Perihsemal Spaces.The principal account of the circulatory system in this family

of Oligochseta—and that is very incomplete—is contained ina paper upon E u d r i l u s by myself (15). The blood-vesselsof L ibyodr i lus are very similar, but I did not find a sub-nervian trunk. Very frequently in transverse sections a blood-vessel could be seen lying beneath the peritoneal membrane,and vertically beneath the nerve-cord j but by following outthe vessel through a few sections it was invariably found to bemerely a part of the integumental blood plexus running for ashort distance in a longitudinal direction. The dorsal vesselis united with the ventral by a series of paired "hearts."These increase in size posteriorly. The dorsal vessel isensheathed by a layer of " chloragogen " cells, beneath whichis a thin layer of very delicate muscular fibrils j the aper-tures of the hearts into the dorsal vessel are guarded byvalves consisting of a mass of granular columnar cells withsmall nuclei; there are similar valves where the heartsdebouch into the ventral vessel. The s u p r a - i n t e s t i n a ltrunk is recognisable only in the oesophageal region of theworm; it is very easily seen in dissections, and its calibreis quite equal to that of the dorsal vessel. The supra-intestinaldiffers from the dorsal blood-vessel in having only a very thinperitoneal layer; there are no large chloragogen cells like thepear-shaped cells which cover the dorsal vessel, only a cover-ing of much flattened cells: the supra-intestinal trunk isunited with the dorsal by a vertical sheet of mesentery. Thesupra-intestinal vessel is directly concerned with the bloodsupply of the oesophagus. As already mentioned, the oesophagealwalls contain an extremely rich meshwork of blood capillaries;in specimens that happen to have been killed with this partof the vascular system naturally injected, the walls are renderedturgid by the contained capillaries, which have almost theappearance of forming a continuous sinus; here and there thesupra-intestinal vessel is connected with this network by ashort tube.

The presence of infra-oesophageal vessels has been

STETJCTUEB OF EABTHWOBM ALLIED TO NBMBETODEILUS. 551

described by myself in E u d r i l u s j as they occur in L i b y o -dr i lus they will probably prove to be characteristic of thefamily. Similar vessels appear to occur in other earthworms,but their distribution has not been much studied. In L ibyo-drilus as in Eudrilus they are paired trunks, butthey do not unite together at intervals as in the latter genus.These vessels are, like the supra- oesophageal (supra-intestinal)trunk, concerned with the blood supply of the oesophagus ; theyare probably efferent trunks, taking the blood away from theoesophagus, which has reached it by way of the supra-oesopha-geal vessel.

Two mesenteries are connected with these vesselsand with the ventral oesophageal wall; these enclosea space which appears to be completely shut off fromthe ccelom of the segments. The arrangement of thesemesenteries differs in different parts of each segment. Towardsthe middle of the segment, as is shown in fig. 17, the twomesenteries originate from the lateral regions of the oesophagus(the histological details of the oesophagus are not shown in thefigure) ; they are thrown into folds by the contraction causedby the preserving fluid. These mesenteries unite considerablyabove the ventral blood-vessel, and thus enclose a space whichis roughly crescentic in outline but of considerable verticaldepth. The membrane consists of a faintly staining nearlyhomogeneous core, covered on both sides by peritoneal cells,of which the nuclei were alone visible; here and there smallgroups of longitudinally running bands of muscular fibres, notshown in the figure cited, are embedded in this homogeneouslayer. The figure, however, does show two longitudinallyrunning bands of muscle (m); these are special musclesattaching the ventral surface of the oesophagus either to thesepta or to the ventral parietes. Above these, i. e. nearer to theoesophageal wall, are the paired sub-oesophageal trunks (bl.ves.);in the section represented in the figure the two blood-vesselsare seen to be attached to the mesenteries, but in other sec-tions they lie freely within the mesenteries, and further backthey may come to lie outside. These facts appear to show that


we are dealing here with a perihsemal coelomic space not foundin connection with supporting mesenteries of the blood-vessels;further forward in the segment the two lateral membranescome to be attached to the intersegmental septum where thisforms the floor of the perihsemal chamber. The supra-oeso-phageal vessel is for the most part not enveloped in a peri-hsemal space, but it is connected in parts by the membraneswith the walls of the oesophagus; these gradually shift theirareas of attachment to the oesophagus until they are nearlycontinuous with the two membranes which enclose the sub-cesophageal vessels.

The formation of peribsemal spaces is an interesting, butnot a perfectly new fact in the anatomy of Oligochseta,

I believe that I was the first to call attention to the factthat, in an earthworm (Deinodri lus) belonging to quite adifferent family, the dorsal vessel is for the greater part of itscourse enclosed in a " pericardium." An almost identicalstructure has been figured by Professor Spencer in Mega-scol ides aus t ra l i s . It is noteworthy that in both thesecases the " pericardium " contains abundant perivisceral cor-puscles which stain deeply, and appear to be merely theyounger forms among the corpuscles of the perivisceral fluid.I suggested the possibility of these corpuscles being principallyformed in that space.

Similar corpuscles occur in the space which surrounds thesupra-cesophageal vessel in Hype r iod r i l u s and Hel io -dr i lus , and I have found them in L ibyodr i lus . I did not,however, observe any proliferation of these cells from the liningmembrane of the perihsemal space in L i b y o d r i l u s ; therewere simply masses of these cells (fig. 17, corp.) lying here andthere within the space.

Fig. 21 represents the course of the sub-cesophageal vesselsin Segments 9—11.

They generally lie at some distance from the oesophagealwall, and are connected at frequent intervals by branches withthe peri-cesophageal plexus. Towards the anterior part ofSegment 9 the two trunks are connected by a branch which


was prolonged backwards and downwards to the neighbour-hood of the ventral vessel; this branch (a) does not, however,open into that vessel, but runs into one of the muscular bandswhich unite the oesophagus with the parietes. Farther backstill each vessel gives off a branch which supplies the inter-segmental septum ; here its capillaries no doubt unite withthose of branches of the ventral blood-vessel. In the 10thsegment there was no connection between the two sub-ceso-phageal trunks; each of them gives off a branch (a) whichsupplies the muscle (m.) running from the oesophagus to theparietes.

These branches pass along the walls of the perihsemal spaceand reach the interior of the muscle, along which they pass toits point of insertion j these two branches, of course, cor-respond to the single cutaneous branch which I have describedin Segment 9. At the septum dividing this segment from the11th a branch is given off from each vessel, which supplies notonly the septum but also the sperm-sac. In the next segmentthe branches of the sub-oesophageal vessels are the same, andtherefore need no description. I imagine that these sub-cesophageal vessels represent, wholly or in part, the lateraltrunks1 of other earthworms, which appear at least frequently,if not always, to take their origin from the peri-cesophagealblood network.

§ Nephridia.

In dissecting the worm the nephridia were quite obvious inmost of the segments of the body; and where visible, pre-sented a paired arrangement which characterises all theEudrilidse. In the posterior region of the body the nephridiawere particularly conspicuous, both in fresh and alcoholicspecimens, by reason of their opaque white coloration. Inthe anterior segments of the body the nephridia were largelyadherent to the posterior septum of their segments, and didnot show the white opaque appearance of the posteriornephridia. We have evidently here another instance of what

1 "Intestino-tegumentary."

554 PRANK E. BEDDARD.

is very common among the terrestrial Oligochseta, viz. a sepa-ration of the nephridia into two series, an anterior and aposterior; this is seen, among other forms, in Pontodri lusand in Microchseta. In the segments occupied by thespermatheca, viz. in Segments 13—17,1 no trace of nephridiacould be detected in a dissection. I am disposed to referthis partial obliteration of the nephridia in this region ofthe body (we shall see immediately that they have not abso-lutely disappeared) to the enormous development of thespermathecal sac, which occupies most of the available space;the case is, in fact, analogous to that of many aquatic formsin which the nephridia disappear with the appearance of thegenital organs.

Each nephridium (fig. 11, /.) has a funnel lying, as usual,in the segment anterior to that which bears the externalpore. The nephridia of the posterior segments are enve-loped by a mass of peritoneal cells; such at least appearsto be the nature of the very peculiar tissue illustrated infig. 10, c. I may remark here that both Heliodri lus andHyper iodr i lus have a similar investment to the nephridia.A covering of this kind which is simply an exaggeration of theordinary peritoneal layer is very characteristic of the aquaticOligochseta, but it has before now been recorded in earth-worms ; it was first described in an earthworm by Perrier inPontodri lus .

In sections of Libyodr i lus which have been stained withborax carmine this mass of cells is very deeply coloured; thestaining fluid has, however, chiefly affected not the protoplasmof the cells, but innumerable spherical particles with whichthey are crowded. Among these deeply-stained spherules aremasses of others, rather larger, which are not stained at all(cf. fig. 6, c'.). The cells were not, however, alwaj^ foundto be loaded with the products of their activity; occasionallythe nephridial tube is embedded in a mass of deeply-stainingcells, of which the nuclei were very conspicuous ; the out-

1 There was some variation, probably due to different stages of maturity,in the number of segments from which nephridia were apparently absent.


lines of the cells were not in every case so clear. Compara-tively few of the cells contained agglomerations of secretedspherules. The worm which furnished the material for thesection described here was immature; but it must not be inferredfrom this that the activity of the glandular cells surroundingthe nephridia does not commence until the animal is fullymature; in the youngest individual which I have been ableto study the cells in question were crowded with spherules.Their activity is evidently intermittent.

In fig. 11 are represented three successive nephridia fromthe post-clitellar region, belonging to as many segments.The nephridia themselves are opaque white bodies, broadertowards the middle line of the body as there represented; onthe upper surface it is quite easy to see, even without using alens, a single loop which appears darker than the surroundingtissue on account of the thinness of its walls. This part ofthe nephridium will be referred to in connection with theminute structure of the glands. A narrow tube leading fromthe broad end of the nephridium and perforating the septumtraced in the funnel, situated in the segment in front, is quiteeasy to make out; so is another tube which passes direct tothe body-wall in front of the ventral pair of setae; this tube isthe external duct of the nephridium. Anyone who was con-tented, as were some of the earlier investigators, with dissec-tion only, would be satisfied that in such a drawing as fig. 11the nephridium was sufficiently displayed. The nephridiumitself is shown, the funnel and the duct leading to the exterior.But there is apparently no external orifice corresponding to theplace where the duct appears to perforate the body-wall onits way to the exterior.

In examining the body of the worm with a lens I did notsucceed, as already mentioned, in discovering the nephridio-poresj which are generally quite easily visible, even without alens.

This failure to find the nephridiopores was at once accountedfor when I examined a fragment of the cuticle stripped off andmounted in a drop of water.

556 FEANK E. BEDDAED.

Besides the minute orifices of the unicellular glands of theepidermis (fig. 3), which here, as in other species, show across-like form illustrated in many memoirs upon the anatomyof earthworms, there were other larger orifices of a circular orperhaps slightly elliptical form. In the figure cited the numberof these apertures relatively to those of the unicellular glands isshown; they are extremely numerous in each segment, and haveno particular regularity of arrangement.

These apertures obviously suggest the external pores of thenephridia, which are so numerous in Perichseta and otherforms with diffuse nephridia. In Perichseta the aperturesin question are of moderate size, though considerably smallerthan the apertures through which the setae protrude. Theyare continuous with a little cylinder of chitinous membrane,which is, of course, the lining of the nephridial tube.

In L ibyodr i lu s the apertures that I have referred to weresmaller than those ofPerichaeta, and I could not detect theinvolution of the chitinous membrane. Otherwise I shouldhave thought myself justified in stating, if necessary withoutany further investigation, that L ibyodr i lus belonged to thatgroup characterised by a diffuse, irregular nephridial system.

This suggestion, however, appears to be somewhat at variancewith the statement that L ibyodr i l u s , like other Eudrilids,possesses paired nephridia, one pair to each segment. I havefound, however, by a series of sections, that the body-wall ispe rmea ted by a system ofbr an ching and anastomosingcanals, opening on to the exter ior by numerous aper-tures , and connected on the o ther hand with thepaired nephr id ia . I took these canals at first for blood-vessels, to which they bear not a little resemblance j indeed, Iam still unable to find any very marked histological differencebetween these tubes and the blood-vessels. That they belongedto a different system was shown by the fact that they werefrequently found to be accompanied by blood-vessels. It ishardly perhaps necessary to say that there was no connectionbetween these tubes and the blood capillaries; the former nevercontained blood-clots, while it was impossible to follow out a

STRUCTURE OP EARTHWORM ALLIED TO NEMERTODRILTJS. 557

blood-vessel through more than two or three consecutivesections without finding coagulated blood in its interior; andit is not difficult in well-preserved earthworms to detect theblood-clots, nor is it easy to confuse them with any otherstructures as a general rule.

The tubes that I have referred to consist of larger trunkswith a definite arrangement, and smaller vessels which form aplexus; the longitudinal and circular muscular coats were per-meated by them. It is, perhaps, necessary to explain herethat the tubes in question have nothing to do with the" Lyraphspaltraume " which Dr. Kukenthal has figured anddescribed in certain Oligochseta, particularly in Tubif ex j Ihave met with spaces similar to those, and crowded with lymph-corpuscles, in various genera of earthworms. I found them tobe particularly abundant in the two genera Hel iodr i lus andHyper iodr i lus described in a recent number of this Journal(1). They consisted in those genera, as Dr. Kukenthal haspointed out for other forms, of spaces, with no special walls,between the muscular fibres. I quite agree with Dr. Kuken-thal in regarding these as the first beginning of the lymphaticsystem of the Vertebrata, in which group the finest branchesof the lymphatic system are without intrinsic walls. Thetubes which I describe here have definite though thin walls,darkly stained by borax carmine j the substance of which theyare composed is granular in appearance, and there are evidentnuclei attached here and there to the outside of the walls. Theprincipal trunks run in a longitudinal and a transverse direc-tion; there are four main longi tud ina l t r u n k s , whichr u n on a level with the four pai rs of setae; they arecon t inuous from segment to segment.. These tubes are of considerable calibre, almost equal indiameter to one of the setse, or even greater; it is not particu-larly useful to give accurate measurements of them, for thereason that they varied considerably in size from place toplace, contracting here and expanding there. Their walls arethin, but quite as thick as those of blood-vessels of about thesame size,

558 FBANK E. BBDDAED.

The longitudinal muscular coat consists, like that of otherearthworms, of fibres embedded in a matrix of connectivetissue. As I have already mentioned (supra, p. 545), this con-nective tissue forms a thickish layer below the level where themuscular fibres end; it is in this layer that the longitudinalvessels run. At the implantation of the couples of setae thelongitudinal vessels come to lie within the arch formed by thetwo setae—which converge at their deep ends, and diverge super-ficially. Just behind the setse the longitudinal vessel gives off awide branch, which gradually gets nearer and nearer to the thinperitoneal epithelium. Ultimately (fig. 7) it comes to lie withinthe body-cavity, surrounded at first by a prolongation of thealmost hyaline connective tissue of the longitudinal muscularlayer. This covering finally disappears, and the tube comes toan end ; in a few cases I have traced it into connection with avery rudimentary coil of nephridial tubules. I have alreadymentioned that in the clitellar segments the nephridia are notvisible with a lens. The tube lying within the coelom wasalways accompanied by a blood-vessel of about the same dia-meter, and I have observed the two to be suspended by acommon mesentery. The longitudinal vessels are also pro-vided with numerous branches, which pass among the longi-tudinal muscles; some of these branches are smaller, somelarger; a few of the larger ones pass obliquely upwards in thedirection of the circular muscular layer ; the tract which thesebranches traverse is free from muscular fibres; t raced up-wards, these branches are seen to open into a c i rcularvessel, which runs r ight round the body; these circularvessels, which are repeated metamerically, lie just between thecircular and longitudinal muscular coats, close to an importantnerve, which also passes right round the body (see fig. 20).The circular vessels are of considerable width, and can be easilyrecognised in sections examined by quite low powers; theiroutline is somewhat crenated, which probably means that theycan be expanded or retracted in accordance with the move-ments of the body. The fact that the vessel lies between thetwo muscular coats, instead of within the substance .of one of

STRUCTURE OF EARTHWORM ALLIED TO NBMERTODRILUS. 559

them, probably ensures less injury through pressure. Thesetubes, like the rest, appeared to be entirely empty, or, at anyrate, to be filled with an absolutely clear fluid j they give offnumerous branches on all sides; the commencement of thebranches, which run along the segmentsfromend to end—that is,in a longitudinal direction—could be seen in transverse sectionsas elliptical foramina in the walls of the tube (see fig. 14). Thebranches which pass downwards ramify among the longitudinalmuscles, and even on the dorsal side of the body of the worm.Where there are no conspicuous longitudinally-running trunksthe branches reach the thick layer of connective tissue whichlies to the inside of the longitudinal muscles; arrived there,they pass in different directions, longitudinal as well as trans-verse. Besides the main transverse trunks running betweenthe two muscular coats I observed vessels of less calibre, run-ning, as shown in the diagram (fig. 16, a), just below the peri-toneum, and apparently continuous right round the body.

The branches which pass upwards could be traced as far asthe epidermis; they were constantly, like the other branches,accompanied by blood-capillaries. I could not detect theactual orifices, but at frequent intervals the non-glandular cellsof the epidermis were closely crowded together. At thesepoints I imagine lie the external orifices which are so evidentupon the cuticle when it is stripped off and examined.

In no case were cilia observable along the course of thetube. It is clear that this system of tubes forming a plexuswithin the muscular coats or the body-walls is a new form ofexcretory organ, and unlike any that has been hitherto describedin any Oligochsete.

A plexus of nephridial tubes, not interrupted by the septa,occurs in a good many forms;" but it has been hitherto foundto lie in the coelom, or is at most partly retro-peritoneal;besides, in the genera (Perichaeta, Megasco l ides , &c.)which have excretory organs of that pattern the tubes are tosome extent ciliated; in those forms there are numerousexternal pores, and so the integument is perforated by numerousnephridial tubes. These may even branch on their way to the

560 tfRANK E. BEDDABD.

exterior, as I have figured in Acanthodr i lus (2, pi. xxx,fig. 1), and as Prof. Spencer has figured in Megascolidesaus t ra l i s (9, pi. vi, fig. 21); but there is no branchingand anastomosis combined, such as is described above inL i b y o d r i l u s ; in Perichseta, &c, the network is confined tothe coelom, and is formed out of the proximal part of thenephridia; in L i b y o d r i l u s the network is in the thickness ofthe body-wall, and is formed out of the distal part of thenephridia. It has been already explained that the pairednephridia of the clitellar segments become rudimentary,though they do not entirely disappear; if the ccelomic part ofthe nephridia were to disappear—and they have all but doneso in the clitellar region—the nephr id ia l system wouldconsist merely of a r ich ne twork of smaller and l a rge rtubes in the th ickness of the body-wall.

The figure (fig. 14) which illustrates the arrangement of thisportion of the excretory system represents a combination ofseveral sections. It should be stated, however, that it is notmeant as a diagram ; such an arrangement as is there depictedmight well occur and be visible in the thickness of any onesection. To thoroughly demonstrate the network in the longitu-dinal muscular layer probably needs some process of injectionwhich I have not been able to apply. Had I been aware ofthis interesting network of fine tubes in the skin I should havecertainly attempted some injection while I had living speci-mens at my disposal. As it is, I am inclined to think that Ihave not in my drawing done full justice to the complexity ofthe mesh work; the scheme (fig. 16), which is purely diagram-matical, expresses my idea as to this network. In fig. 14 twolongitudinal ducts (d) are shown, and the connection of eachwith the circular vessel; the latter (c) is represented as cut atdifferent levels; the thickness of the walls of the tubes ramifyingamong the longitudinal muscles is, perhaps, rather exag-gerated. At a a branch of the longitudinal trunk d is seento leave the muscular layer, and to project into the body-cavity,still surrounded by a connective-tissue sheath; this branchjoins one of the paired nephridia.

STEUCTURE OF EARTHWORM ALLIED TO NEMERTODR1LTJS. 561

Fig. 7 represents one of the longitudinal trunks seen inlongitudinal section; it runs for the greater part of its coursein the thick layer of gelatinous tissue which bounds the longi-tudinal muscles below; at the implantation of the setee itpasses up into the muscular layer itself. These vessels, aswill be seen from the figure, have a somewhat undulatingcourse; they are occasionally diverted by a large blood-vessel.I have not shown in this figure many branches passingfrom the longitudinal trunk, because these were not visible,exoept at a, in the section of which it is a drawing. AtN the duct of a nephridium is seen to join the longitudinalvessel. In the anterior segments of the body the ducts of thenephridia pass down in close contact with the hinder septumof their segment to join the integumental network; in theposterior segments, as is shown in fig. 7, they are not insuch close relation to the septum.

A connect ion of t he nephr id ia with the pha rynxoccurs in this earthworm. The ventral wall of the pharynx,as in other Oligochseta, is formed of but little more than thelining epithelium ; the dorsal wall, on the contrary, is extremelythick, owing to the mass of muscles which overlie the epi-thelium. Here and there the epithelium of the ventralpharyngeal wall gives off very short tubular diverticulawhich are connected with nephridial tubules; these samenephridial tubules can be traced in the other direction into thelongitudinal vessels of the body-wall and so to the exterior(fig. 15).

An opening of nephridia into the stomodseal region of thealimentary tract in earthworms was first discovered by myselfin Acan thodr i lus m u l t i p o r u s ; subsequently Spencerfound numerous nephridial apertures into the pharynx inMegascol ides .

In fig. 15, the opening of a tubule into the ventral side ofthe pharynx is shown; these apertures are not numerous, andappear to be regularly paired ; the epithelium of the pharynxdips down, its cells gradually getting shorter; the nephridium,into which this short diverticulum opens, forms a coil within a

VOL. XXXII, PART IV.—NEW SBR. P P

562 FRANK E. BEDDABD.

layer of connective tissue and muscles belonging to thepharyngeal wall.

The development of these nephridia, so far as I have beenable to trace it (see on p. 574), seems to indicate that thenetwork in the body-wall is a secondary arrangement. It isundoubtedly necessary to be very careful in arguing from on-togeny to phylogeny, but so far as the facts go they seem topoint in this direction. In this case it will be hardly permis-sible to compare the network to that of flat-worms, particularlyof Cestodes; in the Cestodes the nephridial network appearsto exist not only in the mesoderm, but also immediatelybeneath the cuticle in the layers of the body-wall.

On the other hand, it may be permissible to compare thesestructures with something of the same kind in the Nematoids.These worms usually possess at least remnants of a ccelomwhich is well developed, and with a limiting epithelium inGordius; 1 in Ascaris, Joseph has stated (' Zool. Anz./ Bd.v, p. 603) that it is possible to inject from the excretory porea fine system of canaliculi lying between the muscle-cells, andin fact pervading the body generally, while Schneider (Mono-graph Nematoden) has figured the branches in Ascar is . Inany case the canals running in the lateral lines are not a littlesuggestive of the longitudinal canals which I have described inL ibyodr i lu s . In the Acanthocephala also, where there is acoelom, the lemnisci, which have been stated to occur in certainNematoids also by Hamann, appear to be processes of thebody-walls depending into that coelom; they are permeated bytubes which are connected with a system of vessels in thebody-walls. These tubes may be excretory in nature, thoughthey have been described as vascular. In any case I am notaware that a similar network of tubes has been described inthe integument of any Oligochaeta; this worm, therefore, has

1 According to Vejdorsky's recent work upon the structure of Gordius(' Zeitschr. f. wiss. Zool.,1 Bd. xliii) these Nematoids show many points ofaffinity with segmented worms; so much so that they should be removedaltogether from Nemathalminthes. The excretory organs appear to be repre-sented by coelomic canals.

STEUOTUBE OP EARTHWORM ALLIED TO NEMERTODRILTJS. 568

an excretory system which is at least of interest in beingformed on quite a novel plan.

§ Male Reproductive System.The testes are paired structures lying in Segments 10 and

11; they are not enclosed in any sacs, and are quite indepen-dent of the sperm-sacs. The gonads are remarkable on accountof their great length and thinness; the extremities are frayedout, as is usually the case among earthworms, into a number of

Sperm-sacs.—There are two pairs of sperm-sacs attachedto the anterior walls of Segments 11 and 12; each sac of eachpair is quite independent of its fellow. In the living wormthe sperm-sacs have a whitish appearance with the exceptionof the basal part, which is greyish brown. In this part of thesac the Gregarines, which appear to be parasitic in all earth-worms, are chiefly lodged, and the colour is due to brown pig-ment deposited round their cysts. As to the histologicalstructure of these sacs, they agree with those of other earth-worms in having their cavity greatly broken up; the sperm-sacs on their first appearance are solid, except for a very smallcavity which communicates with the interior of the segment infront of that in which they lie. There are no seminal reser-voirs, and thus the testes, and funnels of the vasa deferentia,depend freely into the ccelom.

Sperm Ducts and Funnels.—In all the members of thefamily Eudrilidse (excluding from this family Eudriloidesand Pygmseodrilus) with the exception of Nemertodrilusgriseus, and perhaps Preussia siphonochseta, the spermducts are dilated before their connection with the funnel.In Liby odrilus there is no such widening of the sperm ductseither in the neighbourhood of the funnels or anywhere else.The funnels themselves occupy the usual position in Segments10 and 11; those of Segment 11 are more nearly opposite tothe sperm-sacs than to the testes; the sperm ducts are narrowtubes of the usual appearance, but are unusual in passingthrough the segments which they traverse at some distance

564 FRANK E. BEDDAED.

from the body-wall; their course is straight without anywindings; the two sperm ducts of one side appear to unitejust behind the intersegmental septum 12—13 ; as a matter offact they do not unite here or anywhere else until at theiractual orifice; they lie, however, in close contact. In trans-verse sections the sperm ducts are seen to have quite theordinary structure; there is no development of muscular fibresround them such as occurs in Eudr i lu s . The funnels arelarge and their walls are much folded.

The a t r i a have the tubular form which is characteristic ofthe family; but they are short, and usually contained entirelywithin the 18th segment. Towards the external aperture theybecome narrower. These organs have the " nacreous" appear-ance of the corresponding organs in Eudr i lus , which is duein both cases to the great development of the muscular coat.This reaches an extraordinary thickness in L ibyodr i lus ,which is thus remarkable even among the Eudrilidse.

The external orifice is single, and is situated upon the summitof a rounded elevation occupying the middle of the ventralsurface of the body and extending over a portion of Segments17 and 18. The epithelium which covers this elevation is fur-nished with numerous glandular cells, conspicuous on accountof their dark staining. With each atrium is connected a sacin which lies a single short penial seta. The sac communicateswith the distal part of the atrium that is embedded in thethickness of the body-wall.

The penial seta is illustrated in fig. 8; it is remarkableon account of its shortness and its blunt rounded free extremity,which is not ornamented.

The atrium is lined throughout with epithelium, which isseparable into two strata.

The cells, however, had not in any case (I examined theatria of three individuals) the extremely glandular appearanceof the corresponding epithelium in Eudr i lu s. This may, nodoubt, be owing simply to a cessation in the secretory activityin the cells.

In nearly all the Eudrilidse the vasa deferentia open into the

STRUCT ORE OF EARTHWORM- ALLIED TO NEMERTODRILTJS. 565

atrium. Perrier, who was the first to make known the struc-ture of Eudrilus, described the vasa deferentia as openinginto a pouch, into which also opened the atrium, regarded byhim as the equivalent of the prostate of other earthworms.It is so figured in his memoir (10, pi. ii, fig. 26). I myselfshowed that, unless we were dealing with different forms, thisdescription was incorrect; in specimens of Eudrilus comingfrom several distinct localities I found that the vasa deferentiaopened into the structure that had been termed prostate. Thisglandular tube, I pointed out, was itself divided into twoseparate tubes by a longitudinal septum not visible or hardlyvisible externally. Into the longer of the two tubes, at a pointcorresponding with the apex of the shorter compartment, openthe vasa deferentia, each by its own orifice. The structure ofEudrilus has been recently reinvestigated by Dr. Horst (7),who gives a diagram (7, p. 6) agreeing with my figure (15, pi.xxxiii, fig. 15), and remarks that "l'appareil genital male estexactement conforme a la description detaillee quiM. Beddaxda publiee de cet organe."

In Teleudrilus Rosa describes the opening of the vasadeferentia into the atrium not far from the anterior extremityof the latter, i. e. not far from their point of opening on tothe exterior. The same thing occurs in Heliodrilusand Hyperiodrilus; in Nemertodrilus the communica-tion between atrium and vasa deferentia takes place, as itapparently does in Teleudrilus, not far from the externalaperture of the former.

In Libyodrilus the arrangement is very interesting. Ona dissection of the worm I could not follow the course of thevasa deferentia beyond the point of opening of the atrium;this was due to the fact that the two tubes, which retain theirdistinctness though they are in very close juxtaposition, atthat point perforate the muscular tissue of the atrium; theypass up, at first within the thickness of the muscular tissue, andlater within the epithelium, to nearly the summit of the atrium.At this point they open into its lumen by a common orifice;the two vasa deferentia unite just at the orifice ; the cilia are


not continued on to the epithelium which lines the atrium.At the orifice of the vasa deferentia they are particularly long,and project for some way into the interior of the atrium. InLibyodrilus, therefore, the atrium has come to be, as it is insuch worms as Nais, a kind of continuation of the vasadeferentia. Among the Eudrilidse the point of opening of thevasa deferentia gradually moves down the atrium until, inNemertodrilus, . i t comes to be placed near to the externalorifice.

This series of facts lends further support to the originalsuggestion of Vejdovsky, which was strengthened by my ownobservations, as to the homology between the atrium of theaquatic genera and the prostates of the terrestrial genera.

If we are to follow Dr. Benham (11) in objecting to thisidentification we shall be plunged into obvious difficulties, forDr. Benham considers "that a portion of the prostate inPerichseta, Eudrilus, and other genera, in which the spermduct and the prostate join, is probably the homologue of theatrium of Tubifex."

I should mention that the interior of the atrium in Libyo-drilus is not divided by a septum, and that the lining epithe-lium is greatly folded ; this is carried to such an extent that inlongitudinal sections the lumen appears to be furnished withtubular diverticula; transverse sections are required to showthat these are merely foldings of the epithelium.

§ Female Reproduct ive System.

The extraordinary development of ccelomic pouches in con-nection with the different parts of the female reproductivesystem is the most distinguishing character of the Eudrilidse,and also occurs in the present species.

Spermathecal Sac.—In dissecting the species whichforms the subject of the present memoir, the most conspicuousorgan of the body is a large sac which lies upon the dorsalsurface of the oesophagus. This structure is illustrated infig. 1, which represents a general view of such a dissection, and

STRUOTTJBE OF BABTHWOBM ALLIED TO NEMEETODEILUS. 567

more diagrammatically in fig. 9; the latter figure shows therelations of the sac to neighbouring organs. The sac is of abrownish-yellow colour, and of an irregular elongated form;it is marked here and there by furrows, which indicate that itis capable of being extended to a much greater size; it com-pletely covers the dorsal vessel and oesophagus, to which it isattached by a series of thread-like ligaments. The sac extendswhen fully developed from the anterior boundary of Segment13 to the posterior extremity of Segment 18 ; it gives off oneither side three diverticula; from the first pair of thosediverticula arise the oviducts which pass outwards so far asalready stated upon the 15th segment. Anteriorly the sacdivides so as to embrace the oesophagus, round which it formsa ring; immediately beneath the oesophagus the two halvesbecome reunited, and pass forwards and downwards in closecontiguity to the septum separating Segments 12 and 13. Inthis region the sac is very much narrower ; at the nerve-cordthe sac again divides so as to surround the cord, and the un-paired duct which arises from this perineural ring opens on tothe exterior in the 13th segment. The sac was found to befilled with bundles of spermatozoa of irregular shapes andsizes; a fragment of this sac taken from the living ovum andteased up upon a slide showed that it was lined with peculiargranular cells. The cells are so easily detached that it appearedas if they were free in the interior of the sac; an examinationof hardened material showed that this was not so, and that thecells form a lining to the sac. The fresh cells are of an irre-gular, generally somewhat elongated form; occasionally theyare branched; the protoplasm of the cell is very clear andtransparent; in the protoplasm are a quantity of spheroidalgranules, usually massed together in the widest part of thecell; the cells resemble very closely the peritoneal cells whichcover the alimentary tract, but the granules in their interiorare greyish instead of brownish green.

In sections of the mature spermathecal sac (see fig. 12)i-ts walls are seen to be muscular, with a coating and lining ofepithelium.

568 FRANK B. BEDDAED.

Embedded in the thickness of the muscular coat is a denselayer of tissue which stains darkly; this layer is of some thick-ness, but apparently homogeneous throughout; here and there,for instance, in that part of it which covers the egg-sac asshown in fig. 12, favorable sections demonstrate that it isa membrane, el; it is usually much bent, showing the zigzagcontour illustrated in the figure; in all probability it isof the nature of elastic tissue, and permits of the easy recoveryof the original dimensions of the sac after it has been undulydistended with sperm.

The lining epithelium of the sac is, as a rule, more than onecell thick; there appears usually to be an innermost layer offairly regular smallish cells; here and there an extensive pro-liferation of these has taken place. The whole character ofthe cellular lining of the sac indicates that it is not formed as aninvagination of the epidermis; nor, as will be seen later, isit. It has been said that the anterior wall of the sac passes inclose relation with intersegmental septum 12—13. Inlongitudinal sections—which are, I may remark, much moreuseful for studying the structure of worms than trans-verse sections—the anterior wall is seen to be not merelyin continuity with the septum ; it is formed by theseptum itself.

Ovaries.—I could not find the least trace of these organsin fully mature worms, either by dissection or in sections.That the ovaries should be evanescent structures in an earth-worm is rather unexpected. They are present in young stages,where they exhibit the usual position and structure, thoughlike the testes they are much elongated and very narrow.

Egg-sacs.—In a dissection the egg-sacs can hardly be dis-tinguished from the great unpaired spermathecal sac in whichthey lie j a careful inspection shows that at the point wherethe oviduct arises there is a slight bulging outwards ofthe sac; this has a browner coloration than the rest ofthe walls of the sac. This, however, is no more conspicuousthan is represented in fig. 9, where the spermathecal sacand the oviducts are displayed in a slightly diagrammatic form.

STRUCTURE OF EABTHWOEM ALLIED 110 NEMEETODBILTJS. 569

In transverse sections the egg-sac of each side is seen to be aspherical body lying within the spermathecal sac, and supportedat one side by the wall of this sac; its cavity, however, isnowhere continuous with the cavity of the spermathecal sac;the two structures are so far perfectly independent, and appearto be as it were accidentally associated. I shall show later(on p. 574) that there are also embryological reasons forregarding the egg-sac as entirely unconnected with the greatunpaired sac in which it lies. The egg-sac of all earthwormsin which it has.been found, with the exception of the Eudrilidse,lies in the 14th segment, attached to the anterior wall of thissegment. In L ibyodr i lu s there is a septum separating the13th from the 14th segment; but this septum does not traversethe spermathecal sac; hence the egg-sacs do not depend fromany intersegmental septum in the fully mature worm.

In its microscopical structure the egg-sac presents no pecu.Rarities of any particular interest. Its cavity is, as is usualwith this organ, subdivided into numerous chambers, packedwith ova and germinal cells in various stages of development.The walls of the sac are formed largely of muscular tissue withabundant nuclei; the compartments which are formed by in-growth of this layer are also muscular, but seem to be irregularlylined with granular peritoneal cells. The relations of the egg-sac to the spermathecal sac are shown in fig. 12; it will benoticed that it projects into the interior of that sac, and in othersections, taken at a different level from the one figured, itappears to lie freely in the interior of the sac. I t is, however,easy to see from the histology of the parts concerned that theegg-sac is not really within the spermathecal sac; the walls ofthe latter are not perforated; they are merely pushed in bythe egg-sac: these points will be understood by a reference tofig. 12.

The figure shows the egg-sac just where the oviduct opensinto i t ; two parts of the oviduct are shown; the lettering odis placed in the oviduct where it commences to widen out intothe funnel; to the right of the figure lies a section of thenarrower part of the tube. Running round the walls of the egg-

570 FEANK E. BEDDAED.

sac where it projects into the spermathecal sac is a hand of elas-tic tissue (el.), which I have already spoken of in connection withthe spermathecal sac; it will be noticed that this band of tissuedoes not belong to the egg-sac but lies outside it, thus showingthat the egg-sac does not really project into the spermathecalsac through its walls; it is, therefore, unnecessary to state thatthere is not any communication between the internal cavitiesof these organs. They are perfectly independent of each otherthough in very close contact. The egg-sacs have, in fact, thesame relation to the spermathecal sac that the sperm-sacs havein certain earthworms to the " seminal reservoir." Forexample, in Dichogaster the sperm-sacs are enclosed in largethin-walled seminal reservoirs. Bergh distinguishes these sacsin Lumbricus as " Samenkapseln" ( = seminal reservoirs),and " Samenblasen" (= sperm-sacs). The former may, andgenerally do, enclose other organs, e. g. the ventral blood-vessels, and, in Dichogaster, the sperm-sacs themselves.

The mature ova have a thick, darkly-staining membrane,in which I could find nostrisesuch as occur in Hyperiodri lusand Heliodri lus .

Oviduct.—In describing the external characters of this•worm, I have already remarked upon the abnormal positionof the oviducal pores. Their position is seen in longitudinalsections to be rather less abnormal. This is due to the factthat the septum which separates Segments 14—15 is attachedto the middle of the latter segment, just in front of thesetEe; accordingly the oviducal pores are really situatedwithin the fourteenth segment, reckoning by thesepta and not by the external furrows; they are, how-ever, as in Teleudrilus, just in the boundary line betweenthe two segments.

In dissections of the worm (see fig. 1) the oviduct isseen to pass in a straight line without any windings from theegg-sac to the exterior; its length is considerable when com-pared with the oviduct of Lumbricus, for example; in dissec-tions the egg-sac cannot be seen, as it is entirely enclosed bythe spermathecal sac. In transverse and longitudinal sections


of the genital region of the worm the oviduct is seen to beensheathed in a tolerably thick muscular coat, as is the casewith all other Eudrilidse. In the young the oviduct is con-nected both with the interior of Segment 13 and with the egg-sac in the way that is generally found in earthworms. In theadult worm the large spermathecal sac nearly fills the 13thsegment and encloses the egg-sac, though, as has been alreadysaid, there is no communication between the two. Near to itsopening into the egg-sac the oviduct is invested with a speciallythick muscular coat; it opens into the interior of the egg-sacby a not very extensive funnel; just before its opening into theegg-sac it gives off a narrow branch which passes into thewall of the spermathecal sac, becoming narrower as it proceeds,and ultimately opens into the interior of the sac by a verysmall aperture. The aperture into the spermathecal sac can-not be of any functional importance, since the ovary is anevanescent organ, and there are no ova to be found in the sacof the adult and nearly adult worm. At the point where thebranch of the oviduct opens into the spermathecal sac thewalls of the latter are specially thickened, and project into itsinterior in the form of a rounded pad. The formation of twoopenings from the originally single aperture is, of course, due tothe growth of this spermathecal pouch, which cuts off the open-ing of the egg-sac into the body-cavity, and at the same timethat part of the oviducal funnel which opened in the youngerstages into the egg-sac.

V. Description of some Young Stages.The youngest individual which I examined was rather more

than half an inch in length. I imagine that it could not havelong escaped from the cocoon.

It is quite evident from an examination of this embryo thatthe present species is hatched in a much more imperfect con-dition than either L u m b r i c u s or Acan thodr i l u s , the onlytwo genera of whose development we have at present anyknowledge. In the embryo of Lumbr icus , according toBergh, the testes and ovaries are present while it is still within

572 FEAJSTK K. BEDDABD".

the cocoon; in the New Zealand A can t ho d r i l us m u l t i p o r u s ,whose development I propose to treat of in another paper, notonly the gonads but the funnels of the sperm ducts and ovi-ducts are fully recognisable in advanced embryos extractedfrom the cocoon.

I could not find any trace of the gonads in the young L i b y o -d r i l u s . This may not be enough to prove that they are notpresent in the stage which I examined; but it seems unlikelythat they would have been overlooked had they reached any-thing like the development that these organs have reached inthe corresponding stages o f L u m b r i c u s and A c a n t h o d r i l u s .

The gonads being absent, or at most very slightly developed,it is not surprising that there is no trace whatever to be foundof this duct or of the terminal apparatus with which the ductsare connected. All these structures then appear to be laterdevelopments than in A c a n t h o d r i l u s or L u m b r i c u s .

One of the most striking features in sections of the embryosof A c a n t h o d r i l u s is the enormous quantity of perivisceralcorpuscles present; they are so numerous as to occupy thegreater part of the coelom. The amount of the perivisceralcorpuscles in L i b y o d r i l u s is not at all large. M. d'Udekem(12, p. 31) has commented upon the great abundance of peri-visceral corpuscles in the young Tubifex just escaped from thecocoon.

The immature condition of this stage was also shown by theminute structure of the alimentary canal and by its contents.I thought it possible that I might detect some trace of thepouches connected with the oesophagus, which are so importantand characteristic a feature of most Eudrilidse; but there wasnot the remotest trace visible; the three gizzards were justcommencing to be formed, but they had not acquired anythinglike the proportions which they ultimately assume. In describ-ing the structure of these organs in the adult worm I havementioned that they lie in three consecutive segments, and areseparated from each other by a short, soft-walled segment ofgut. These tracts (cf. fig. 1) are of very much less extentlongitudinally than the gizzards themselves; in the youngest


worm (fig. 18) the reverse is the case ; the interspaces betweenthe gizzard are very much longer than, about three times aslong as, the gizzards.

The intestine is lined by a columnar epithelium, the cells ofwhich are still loaded with spherical granules; they resemble,in fact, the cells of the intestine in the advanced foetus ofA c a n t h o d r i l u s . The interior of the intestine seems to indicatethat the young worm had not yet commenced to swallow thesoil in which it was found; the intestine contained a granularsubstance, which presented the appearance of a coagulatedalbuminous fluid; in this were embedded a large number ofsetse of small size ; the structure of the setae showed that theyprobably belonged to the same species; at least there wasnothing to indicate that they did not. So far as my experienceat present allows me to say, it is not possible to distinguish thesetse of the Eudrilidse from those of the Lumbricidse, and, in-deed, of most other groups of earthworms. The question is,How did these setse get into the intestine of the young worm ?I noticed in the body-cavity of the same individual a fewsetse embedded among the peri-intestinal ccelomic cells ; thesewere evidently setse of the same individual that had becomefreed into the body-cavity; if they can work their way throughthe intestinal epithelium we have an explanation of how theycome to be found in the cavity of the intestine. I t seemsmore probable, however, that they were originally swallowed,and in this case i t a p p e a r s l ikely t h a t t h e cocoon con-t a i n s up to a compara t i ve ly l a t e per iod more t h a none developed e m b r y o ; the individual or individualswhich succeed in reaching' the full term of their developmentmust feed upon the others when alive or upon their deadbodies.

The structure of the gizzard in longitudinal section is shownin fig. 18. The circular muscles appear to be derived fromcolumnar cells, the nuclei of which are shown; whether thesecells are produced by the division of the hypoblastic cells, orfrom the splanchnopleure, which is most probable, I am unableto say. The muscular fibres themselves are arranged in a

574 FEANK E. BEDDABD.

more or less regular fashion along both sides of those cells.The typhlosole is a simple fold.

The integument in the youngest specimens at my disposalwas chiefly interesting on account of the structure of theepidermis and of the longitudinal muscular coat. In the epider-mis the gland-cells are limited to an area in the middle of eachsegment ; it is evidently here that they first appear. In thelongitudinal muscular coat the fibres are embedded in the samegelatinous material recognisable in mature worms, but this isproportionately less in amount, and there is no thick layer ofit separating the longitudinal muscles from the peritoneum.The fibres themselves approximate in their arrangement veryclosely to Lumbricusj that is to say, they are disposed indouble columns, which are not, however, perfectly regular.

The nephridia in these embryos presented features of con-siderable interest. The paired nephridia were recognisable inall the segments after, and including, the fourth; the first pairsare not covered with the coating of peritoneal cells containingnumerous spherules, as are the succeeding pairs. This invest-ment of the nephridia commences gradually, inasmuch as thoseof the fifth pair had only a very slightly developed peritoneallayer, in which, however, the granules of secretion, which staindeeply, were perfectly plain.

The anterior pairs of nephridia are, as also in the adult worm,closely attached to the posterior wall of their segment. Theyare not bound thereto by any mesentery, but lie in actualcontact with the septum. The duct leading to the exteriorpasses down, in the case of the anterior nephridia at any rate,also in close contact with the septum; it is much coiled, andso in longitudinal sections appeared, in every section, cut atright angles to its course. Arrived near to the insertion of theseptum on to the body-wall the duct joined a continuouslongitudinal duct, passing along the first few seg-ments of the body and putting the nephridia of thesesegments into communication with each other. Oneach side of the nerve-cord this duct was found having similarrelations to the nephridia of the segments through which


it passes. The duct is not embedded in the longitudinalmuscular coat or in the peritoneum, but appears to lie in thecoelom.

If this duct had turned up two or three years earlier than ithas, I should have been able to claim it as a discovery of someimportance. The account given by Balfour of Hatchek's state-ments about the developing nephridia of Cr iod r i lu s gaveadditional strength to them, although Balfour considered themto need confirmation, and the apparent confirmation which isgiven by a young, only just out, foetal earthworm would havealmost clinched the matter. The discovery even of Meyer andCunningham that the adu l t Terebella conchi lega is fur-nished with such a longitudinal duct was regarded of thegreatest importance in that connection. As it is, the newfact recorded here has lost a good deal of importance by appear-ing too late. Since Hatchek's paper the aspect of the nephri-dial question has changed. Nevertheless it is of some littleimportance. In Perichseta there does not appear to be, inthe adult at any rate, a pair of distinct longitudinal ductspassing from segment to segment; there is simply the irregularnetwork of each segment which is connected here and therewith that of adjoining segments. Spencer, however, hasdescribed(9) in Megascol ides a u s t r a l i s a pair of longitu-dinal ducts which run from segment to segment, putting thecomplicated nephridial network and the large paired nephridiaof successive segments into direct communication. I t is not yetknown how early these ducts appear in Megascol ides , butit is interesting to notice that they appear at least compara-tively early in the development of L ibyodr i lus . In the adultworm they persist (fig. 7), but their importance is lost in thecomplications of integumental network. For all that I knowthe paired longitudinal ducts may be the first of the nephridialsystem to appear. I very much regret that my material doesnot enable me to settle this question. At any rate, it is certainthat in Libyodr i lus t h e i n t e g u m e n t a l ne twork con-nected with the paired nephr id i a is preceded bypaired longitudinal ducts uniting those nephridia.


In the stage that I am describing here, there was no dis-coverable trace of the integumental network; the externalpores of the nephridia were apparently paired, but as theywere very minute, I may possibly have overlooked other orifices.It should be mentioned that the nephridial funnels exist atthis stage; they lie in a plane considerably above that in whichthe longitudinal ducts lie, and there is, therefore, no chance ofmy having confounded the longitudinal duct with the tubeleading to the funnel.

Genera t ive Organs.—In a specimen without a clitellum,but as large or nearly so as some specimens with a clitellum,the spermatheca was not visible from the exterior; that is tosay, there were no traces that could be seen, even with a lens,of the external pore, which, though small, is quite evident inmature or nearly mature specimens.

Longitudinal sections revealed a very remarkable conditionof the female reproductive apparatus.

The ovaries, receptacula ovorum, and oviducts present thesame arrangement as in more typical genera of earthworms(Lumbricus, for example).

The epidermis in the middle of Segment 13 for a smallspace is different from the rest; this difference, however,merely consists in the entire absence of glandular cells.This modification of the epidermis, which is illustrated infig. 13, first appears in this stage; it is not directly in-herited from the epidermis of the embryo, as yet undif-ferentiated into gland-cells and packing-cells. In the earlierstages which I have already described there is no means ofdistinguishing by the characters of the epidermis the medianpart of Segment 13, which is so marked in the present stage.A complete series of sections through the 13th and neighbour-ing segments showed a small sac (fig. 13) lying immediatelybeneath the nerve-cord and in contact with the body-walls.The walls of this sac are chiefly muscular; it is lined with alayer of cells, of which the nuclei alone were darkly stained;the outlines of the cells themselves were rather hard to makeout, but the epithelium was evidently composed of very low

STRUCTURE OP EARTHWORM ALLIED TO NEMERTODRILUS. 577

cells; these cells had the appearance rather of peritoneal cellsthan of invaginated epidermic cells.

The sac, where it lay beneath the nerve-cord, had a flattenedappearance, as if it had been squeezed between the nerve-cordand the body-wall; its cavity was chiefly developed in a hori-zontal, not in a vertical, direction. I t could be traced roundthe nerve-cord for a short way on each side as a narrowishtube running forwards and backwards in close contact to thethinnish septum which divides the 13th from the 12th seg-ment ; coming into close relation with the base of the ovary,it ended in the neighbourhood of this organ.

Traced in the other direction the sac penetrated the longi-tudinal muscular coat for a short distance, and gave off anarrow tube, ending blindly some way below the circular mus-cular layer: the space between the ends of this tube and theepidermis was crowded with nuclei, but there was no breakthat I could find in the circular layer of muscles, and no in-vagination of the epiblast. The sac is thus entirely closed;it has no communication with the exterior, which might havebeen expected.

The opposite extremity of the sac does not form a closedsac, as indicated in the figure; it appears to do so in somesections, such as the one illustrated in my drawing; a completeseries of sections shows that this sac communica tes freelywith the body-cavi ty . One wall is formed by theseptum which separa tes Segments 13/14, lettered spt;t he opposite wall is t h inne r , and consis ts of a mem-brane, which connects tha t septum with the onebehind; the membrane in question is, however, not attachedto the intersegmental Septum 13/14 for the whole of its extent;it thus forms an aperture which leads into the subneuralpouch.

In specimens rather more immature than the one justdescribed, the relations of the subneural pouch will be under-stood by a reference to figs. 4—6, which represent three sec-tions of a continuous series; those selected for illustrationrepresent the critical points in the series ; the first one (fig. 4)

VOL. XXXII, PART IV.—NEW SEE. Q Q

578 FRANK E. BEDDAKD.

shows the continuity between the subneural pouch and thebody-cavity; the walls are seen to be formed from the interseg-mental Septum 13/14, and form a membrane (S), which, tracedbackwards, comes into continuity with intersegmental Septum14/15. In the second section (fig. 5) the two membranes joinabove the subneural pouch; the third section (fig. 6) is throughthe ventral median line, and the nerve-cord is, therefore, indi-cated. The subneural pouch is seen to lie below the nerve-cord, and in contact with the longitudinal muscular coat of theintegument; the intersegmental Septum 13/14 does not reachthe nerve-cord, and to its free extremity is attached the mem-brane uniting it with the following intersegmental septum.In this specimen the epidermis lying immediately below thesubneural pouch is exactly like the epidermis elsewhere, i. e.the glandular cells are not absent. It will, I hope, be clearfrom the above description and from the figures that the sper-mathecal sac is first of all formed by certain membranes in thecoelom, which become approximated and attached in parts toform a sac. Later on the sac burrows its way towards theexterior, where it appears to be met by a very limited invagi-nation of the epidermis. This mode of formation has a remark-able analogy to the formation of the oviducts in certain ganoidand teleostean fishes. It is very probable that, as I havealready suggested, the second oviduct in Eudr i l u s is formedin a similar way. It will be observed that in early stages theovary comes to lie within the spermathecal sac. If, for somereason or other, the backward extension of the sac werechecked, it would form simply a duct for the ova.

There is also an interesting analogy to the formation of themephridia and genital ducts in Pe rip at us, which have beenrecently so successfully investigated by Mr. Sedgwick.

In a species of Moni l igas ter—M. Houteni—Dr. Horsthas described the oviduct in a way which suggests thatit resembles the early stage of the spermathecal sac of Libyo-dri lus. His description (13, p. 99) is as follows:—"Asstated before, the 12th and 13th septa are placed closeagainst each other j ; these two septa seem to form together on

STBDOTUEE OF EARTHWORM ALLIED TO NEMERTODRILUS. 579

each side a sort of funnelj the inferior part of which communi-cates with one of the pores on the 14th ring. Although theovaries could not be found, I suppose that this funnel mayfunction as an oviduct."

In Nemertodri lus the spermathecal sac is in a conditionof arrested development; it resembles to a certain extent theearly stages in the development of Libyodrilus, but secondarymodifications—in the complicated fringe which surrounds thepores on Segment 13—appear to prevent their performing thefunction of an oviduct. It would be very interesting to havesome information about the development of the large sacs inNemertodri lus, particularly as to whether they originallycommunicate with the egg-sacs or not.

VI. Homologies of the Reproductive Organs in Eudrilidse.

The homologies of the different parts of the reproductivesystem in Eudrilidse are by no means easy to decipher.

It is possible, however, to attack the problems with greaterconfidence in view of the developmental facts that I have beenable to bring forward. Hitherto nothing but the adult struc-ture was known, and that in certain cases evidently imperfectly.It is clear that in many points the Eudrilidse differ greatly fromall other earthworms; and I think that this paper ratheraccentuates the differences than removes them.

On the other hand, I have been able to show that at a certainstage of development the female reproductive system closelyresembles that of more normal genera; the special peculiaritiesof the Eudrilidse are a later formation; this argues for theisolated position of the group, which I have elsewhere urged,but not for its primitive characters ; the reproductive systemmust be looked upon as much modified from that of otherearthworms.

It seems fairly clear that the large unpaired sacs which existin the genera Heliodrilus, Hyperiodrilus, Stuhlmannia,Polytoreutus, Paradr i lus , Preussia, Nemertodrilus,and Libyodri lus correspond in every case. But they are in


this event not spermathecae, except in function. A true sper-matheca, as I have shown, exists in Hel iodr i lus and Hy-per iodr i lus , partly or entirely enclosed by the median sac.In Paradr i lus , too, judging from Michaelsen's figure, thereis a spermatheca of this kind, but apparently not in some ofthe other genera; nor is this structure represented in Libyo-dri lus . In Libyodr i lus the large unpaired sac isobviously a spermatheca in function, for I foundsperm in it, but i ts development shows that it cannotpossibly be compared to the spermatheca of, e. g.,Lumbricus. I t is a mesoblast ic pouch which hasacquired an ex te rna l opening; whereas the spermathecaof Lumbricus are known, through the investigation of Bergh,to be purely epidermic involutions. The homologue of thespermatheca of Hel iodri lus and Hyperiodri lus in Libyo-dri lus appears to be the orifice only of the mesoblastic sac.In this connection the structure of Nemer todr i lus asdescribed by Michaelsen is of great interest. He has described(3), and I have been able (1) to entirely confirm his descrip-tion, a pair of apertures in Segment 13 which lead into theinterior of that segment; they have no connections with thesacs extending backwards from Septum 13—14, but Michaelsenhas suggested that they represent the orifices of those sacs; Iam now of opinion that this suggestion is perfectly correct.So far Nemer todr i lus appears to be a degenerate form, andother structural facts confirm that view. It is a little difficultto understand the arrangement of the various organs inPreussia, since Dr. Michaelsen was unable, through beingobliged to respect museum specimens, to make out the relationof the ovaries.

The following is Michaelsen's description of the parts inquestion : I think it worth while to quote it in full, as thejournal in which it is contained may not be accessible every-where.

" Der weibliche Geschlechtsapparat zeigt wieder eine neueModification der eigenartigen Verwachsung, wie sie fur dieTeleudrilen charakteristisch ist. Die ventral median Offnung


im 15 Segment fiihrt in eine lange, gestreckt birnformigeTasche, die sich bei dem untersuchten Exemplar bis in das 19Segment nach hinten erstreckt. Nach vorne schien der Stieldieser Tasche in zwei grosse, ovale, dunnhautige Blasenueberzugehen, die fast bis an den Anfang des 13 Segmentsreichen. In dem nach hinten gerichteten Pole dieser Blasenmiinden die Eileiter ein. Diese gehen von ihrer Ausmiindungseitlich am 14 Segment, zuerst in grader, senkrecliter Richtungauf die Medianebene zu. Weit bevor sie dieselbe erreichenbiegen sie nach hinten um. Zugleich verdicken sie sichbedeutend. Das Dissepiment 14/15 durchbrechend, verlaufensie nach hinten bis vor das Dissepiment 15/16, biegen sie dannwieder nach vorne um und miinden schliesslich in die erwahntenBlasen ein jeder Eileiter tragt an der ersten Knick-ung, an der tJbergangsstelle von dem engen distalen Teil zu dererweiterten, nach hinten gerichteten Schleife, ein verhaltniss-massig lang gestieltes Receptaculum Ovorum."

It appears to me that the " thin-walled vessels" and the tubeleading to the receptaculum correspond to the first of thediverticula of the median sac in Libyodr i lus , and that thedistal extremity of the " pear-shaped pouch " is the true sper-matheca. It is rather harder to understand Eudr i lu s andTeleudr i lus . The former genus has been redescribed byHorst (7), his description of figures being confirmatory of myown. There seems, therefore, to be little doubt, now that socareful a worker as Dr. Horst has looked into the matter, thatthe adult structure of the female genitalia of Eudr i lus isknown.

I must, in the first place, admit that the structure of otherEudrilids is not confirmatory of my view that in Eudr i lusthere are two pairs of ovaries and two pairs of oviducts. I donot, however, admit that that view is yet entirely disproved.In order to show that the tube, which I have regarded as theoviduct of Segment 13, is not an oviduct, it must be shownthat the organ regarded by Perrier, Rosa, Horst, and myself asa spermatheca is a coelomic sac comparable to that of Hyper io-dr i lus , &c. I am inclined, however, to believe that this will

582 FRANK E. BEDPARD.

be proved ; but then it will have to be farther proved that theduct of that sac up to a point beyond the "oviducal" orificeis also derived from the coelomic sac. Now, Horst says (7, p.232) that the muscular layer of the sperraatheca becomes verythick near to the point of opening of the ovarian duct ( = my" oviduct of Segment 13 " ) . This looks as if the true sperma-thecal invagination began, or rather ended, at this point. Ifso, it would be reasonable to speak of the tube in question asan oviduct, whereas if it were merely a portion of the coelomicsac it could hardly be termed an oviduct, but rather an exten-sion of the said sac forwards.

It is clear that two pairs of ovaries and oviducts formerlyexisted in earthworms; not only do they occasionally occur asa sport (see my remarks upon varieties of Peri onyx), but theyoccur normally in Phreoryc tes . Considerable traces of themissing parts are met with in embryos of Lumbricus andAcanthodr i lus . Dr. Horst has overlooked these facts,someof which were known when he wrote (7, p. 239), " Cheztous les genres d 'Oligochetes, on n'a trouve jusqu'ici qu'unepaire d'ovaires." To return to the immediate subject ofdiscussion, it seems probable that the large sacs termed sper-mathecee in Eudr i lus and Teleudr i lus correspond to thecoelornic pouches of L ibyodr i lus and the other forms. Thequestion is how much of them corresponds; it may probably besafely assumed that up to the point of opening of the ovi-ducts there has been an epidermal invagination ; but beyondthat inference I do not consider it safe to go at present.

VII. Definition of Genus and Species.

Genus Libyodr i lus , F. E. B.1

Nephridia paired, but connected with a network of tubesramifying in the integument; those of some of genital seg-ments disappear in mature worms, but network remains. Alarge unpaired sac opening on Segment 13 extends through

1 T have briefly characterised the species in 'Proc. Zool. Soc,,' 1891, p. 172.

STRUCTURE OP EARTHWORM ALLIED TO NBMERTODRILUS. 5 8 3

five segments and lodges receptacula ovorum; oviducts passfrom these to apertures on 15th segment. Atria two, withthick muscular walls opening by a common orifice on middleline between Segments 17, 18. Each is furnished with asingle penial seta. Vasa deferentia without dilatations ormuscular coat, open near to summit of atria. (Esophaguswithout calciferous glands or ventral pouches; three gizzardspresent at end of oesophagus in Segments 23, 24, and 25.Integument without sense bodies.

L ibyodr i lus violaceus, F. E. B.Setae strictly paired and ventral in position. Penial setse

short with a rounded free extremity. Clitellum occupyingthree segments (14—16). Dorsal vessel single. Colour darkviolet with a tinge of pink.

Habitat—Lagos, West Africa.The above definitions must in the present state of our

knowledge be regarded as only tentative.

VIII. Summary.

The principal new facts in this paper may be briefly sum-marised as follows :

(1) The nephridial system consists of paired nephridiawhich do not open immediately on to the exterior, but areconnected with an extensively ramifying system of tubesembedded in the circular and longitudinal muscular coats;these tubes consist of four principal longitudinal trunks con-tinuous from segment to segment, and of a single large cir-cular vessel in each segment passing right round the worm atthe junction of the circular and longitudinal muscles; theseare connected by a plexus of vessels, and numerous tubules,leading to the exterior, are given off from the circular trunk.In some of the genital segments the paired nephridia havealmost disappeared, leaving only the integumental network.Nothing of the kind has been yet described in any Oligochsete.In the young worm, just escaped from the cocoon, there is no


integumental network, which must, therefore, be regarded assecondary, but the anterior nephridia at any rate are con-nected on each side by a continuous longitudinal duct lyingwithin the ccelom.

(2) In the young worm the reproductive organs agree withthese organs in other earthworms; in the^ adult, a largeunpaired sac lying over the gut is developed; this sac enclosesthe receptacula ovorum, and opens by a median pore on Seg-ment 13. It is developed from mesoblastic tissues, and is nottherefore the morphological equivalent of the spermathecae inLumbr icus , &c, but it performs the same function; the sacis formed internally and then grows out towards the epi-dermis ; it is at first in open communication with the ccelom ;its front wall is formed out of the intersegmental septumbetween Segments 12, 13 ; the ovaries are enclosed by it, butdisappear early, before the sac is completed; otherwise theova would be probably unable to enter the egg-sac whichbecomes nearly completely shut off from the sac; the two arein communication only by the oviducal funnel, which hasbecome divided by the growth of the spermathecal sac intotwo separate tubes, one opening into the spermathecal sac, theother into the closed egg-sac; they unite, of course, to formthe oviduct itself, which opens on to the 15th segment,reckoning by the external furrow, but on to the border linebetween Segments 14, 15, reckoning by the septa.

(3) The testes and the vas deferens funnels are quite typicalin their structure and position; so, too, are the (two) pairs ofsperm-sacs (in Segments 11, 12). The sperm ducts are not,as they are in other Eudrilidse, dilated to form sperm reser-voirs ; they open into tubular atria, with thick muscular wallsand glandular lining, near to their blind extremities; the twoatria open by a common pore upon the border line betweenSegments 17, 18; each is furnished with a short penial setanot ornamented.

(4) The alimentary tract has no calciferous glands orventral cesophageal pouches such as are found in other Eudri-lidre; at the end of the oesophagus are three gizzards, one to a

STBUOTURE OF EARTHWORM ALLIED TO NEMERTODEILUS. 585

segment; the intestine which immediately follows has at firstthree typhlosolar folds; later on the two lateral and shorterfolds disappear. The ventral wall of the pharynx is con-nected with the nephridial tubes of its segments; they openinto the interior of the pharynx.

(5) The area surrounding the setas of each side of the bodyis shut off from the general body-cavity, forming a pairedseries of chambers j in the cesophageal region is developed aperihsemal ccelomic space surrounding the suboesophagealvessels.

EXPLANATION OF PLATES XXXVIII & XXXIX,

Illustrating Mr. Frank E. Beddard's paper " On the Structureof an Earthworm allied to Nemer todr i lus , Mich., withObservations on the Post-embryonic Development ofCertain Organs."

ANATOMY or LIBYODRILTJS VIOLAXEUS, NOV. GEN., N. Sr.

FIG. 1.—Dissection to show the principal organs, t. Testes. Sp. s. Sperm-sacs, od. Oviduct, v, d. Yasa deferentia. at. Atrium. S. Speruiathecalsac. g. Gizzard.

FIG. 2.—Ventral surface of Segments 13—18. sp. Spermathecal pore.? . Oviducal pores. (J. Male pore.

PIG. 3.—Fragment of cubicle, showing nephridial pores («.).FIGS. 4, 5, and 6.—Three figures drawn from a continuous series of sec-

tions, and illustrating the development of the spermathecal sac. Spt. Septumseparating Segments 12,13. S. Hinder wall of spermathecal sac, the cavityof which is lettered Sp. sac. ov. Ovary. N. Nerve-cord.

FIG. 7.—Longitudinal section through a portion of one of longitudinalnephridial ducts, a. Branches given off from duct. iV. Junction with oneof paired nephriuia. The thick gelatinous connective tissue in which the ductis shown ; n. Nuclei of this tissue.

FIG. 8.—Penial setse.FIG. 9.—Spermathecal sac and neighbouring organs. S. Sac. a. Diver-

ticula of the same. r. o. Receptaculum ovorum. od. Oviduct, ces. (Esopha-gus, n. Nerve-cord.

FIG. 10.—Section through a portion of one of paired nephridia. a, b. Ne-phridial tubes, n. Nucleus of same, c, d. Peritoneal investment.

586 FKANK E. BBDDAED.

FIG. 11.—Three nephridia of posterior segments on one side of body, asseen on a dissection. «. Nerve-cord. Spt. Intersegmental septum, nph. Ne-phridium. / Funnel. S. Setse of ventral pair.

FIG. 12.—Transverse section through receptaculum ovorum and spermathe-cal sac. Sp. sac. Spermathecal sac. ov. Ova. od. Oviduct, el. Elasticmembrane surrounding sac.

FIG. 13.—Spermathecal sac at a later stage of development than Figs. 4—6,illustrated by a transverse section through body-wall. Ep. Epidermis, m.Circular muscles. «'. Longitudinal muscles, with lymph spaces (/.). N. Ne-phridial tube. Sp. sac, Sp. sac*. Two portions of spermathecal sac. Spt.Intersegmental septum 12—13. ov. Ovary.

FIG. 14.—Transverse section through body-wall, to show the ramificationsof the excretory tubes. ep. Epidermis, m. Transverse muscular layer.ml. Longitudinal muscular layer. Bl. Blood-vessels. d. Longitudinalnephridial vessels, d'. Smaller tubes, forming network among the muscles.a. Junction with one of paired nephridia. e. Circular nephridial vessel. I.Tube running to external orifice.

FIG, 15.—Section through ventral wall of pharynx, to show opening ofuephridium. o. Orifice of nephridium. ner. Nerve in pbaryngeal epithelium.m. Muscles, nph. Nephridial tubes.

FIG. 16.—Diagrammatic transverse section of body, to show integumentalnephridial network. D. v. Dorsal blood-vessel. S. I. Supra-intestinal blood-vessel. /. / . Infra-intestinal vessels, v. Ventral blood-vessel. Nph. Nephri-dium. /. Longitudinal trunks (four in number) of integumental network.e. Circular trunk lying between circular and longitudinal muscles, a. Cir-cular vessel lying beneath longitudinal muscular layer of body-wall.

FIG. 17.—Transverse section to show perihsemal space surrounding infra-cesophageal blood-vessels {Bl. vess.). ass. (Esophagus, corp. Perivisceralcorpuscles, mes. Walls of periheemal space, m. Muscular bands.

PIG. 18.—Longitudinal section through one of the three gizzards in a veryyoung specimen, giz. Epithelium of gizzard. Per. Peritoneum. Spt.Septum.

FIG. 19.—Transverse section through body-wall, more diagrammatic andless highly magnified than Fig. 14. S. Setae sac. Bl. Blood-vessel. M.Muscle, connecting setse of lateral and ventral couples. Coil. Ccelomic spacecut off from general cavity of segment by membrane Sp. N. Nephridialtube. L. Longitudinal vessel of integumental nephridial network; the net-work is also indicated in white.

FIG. 20.—Highly magnified transverse section to show circular nephridialvessel (».). m. Nerve accompanying it. L. m. Longitudinal muscles.t. m. Transverse muscles.

FIG. 21.—Infra-cesophageal blood-vessels in Segments 9,10,11. a. Branchesof the same. Sp. sae. Sperm-sacs.

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Jltcr. Jownvfl)k.XXXll,N.sM.XXXlX

Documents

On the Structure of a Earthworn m allie tod Nemertodrilus ...These are the only apertures belonging to the genital system which are paired. The male genital pore is unpaired and median;