JOURNAL OF MICROSCOPICAL SCIENCE.

EXPLANATION OF PLATE I,Illustrating G. O. Sars's Paper on Rhabdopleura.

FIG.1.—The animal taken out of the cell and slightly compressed, seen from

the left side.c. Buccal shield.d. Tentacular arms.e. (Esophagus./. Stomach.g. Intestine.h. Contractile cord.I. Hyaline semilunar border at base of tentacular arms.m. The under lip.n. The ciliated tubercle at the base of the tentacular arm.p. The flexor muscle of the tentacular arm.q. The buccal aperture.r. The cellular body between the end of the intestine and the

oesophagus.2.—The animal seen from the ventral side.

(Letters as in fig. 1.)3.—The animal seen from the dorsal side.

(Letters as in fig. 1.)4.—The anterior part of the body seen from in front; c, d, I, as in fig. 1.5.—A part of a living colony magnified about sixteen times.

aa. The cells with their polypides in different states of protrusion.bb. The creeping stem.cc. The buccal shield.eld. The tentacular arms.

ff. The stomach.g. The intestine./(/*. The contractile cord.ii. The axial cord.

6.—A piece of the creeping stem freed from adhering particles, togetherwith the bases of the cells and their polypides mostly strongly re-tracted, about 20 times magnified, showing the single chambers intowhich the stem is divided.

cc. The buccal shield.ff. The stomach.hh. The contractile cord.ii. The axial cord.

7.—The earliest stage of development noticed.8.—A further developed polypide seen from the dorsal side ; cc, the buccal

shield; d, the tentacular arms; h, the contractile cord.9.—The same polypide with the axial cord (»') seen from the ventral

side.

JOUENAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATE II,

Illustrating Mr. C. S. Tomes's Paper on the Development ofthe Teeth, in an Armadillo.

PIG.1.—Section through the lower jaw of a foetal calf, 6 inches long.

a. Meckel's cartilage.b. Dentine germ.e. Enamel organ.d. Process connecting the enamel germ with the deep layer of the

oral epithelium.e. Epithelium heaped up over the situation of the developing tooth.y. Enamel germ of the successional permanent tooth.

2.—From the lower jaw of <x foetal armadillo {Tatitsia Pebd) \\ incheslong.

b. Dentine germ.c. Enamel germ.

3 and 4.—From a foetal armadillo (T. Peba) 3 inches long.b. Dentine germ.c. Enamel germ.j . Germ of permanent tooth.g. Extremity of the cornua of the enamel germ.h. Thin cap of formed dentine.

•—"3

///• & -V$y V/'i'r ?rc <-•<•' 7!Z

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATES III & IV,

To illustrate MM. Van Tieghem and Le Monnier's Researcheson the Mucorini.

Pig. 1.—Section of a zinc box for cell-cultures; it is arranged to holdtwo rows of slides, and is closed above by a glass plate; the bottom iscovered with wet sand or moistened plaster.

Phycomyces nitens.

Pig. 2.—a, spherical spores from small sporangia, the central grannies areyellow; b, fresli, elongated, ellipsoidal or concavo-convex spores from largesporangia; c, older spores, the wall has a double contour; d, older sporesgerminating with rupture of the exospore (x 160).

Fig. 3.—a, spores in process of alteration in a moist medium, the proto-plasm condenses into nodules; b, a germinating hypha in process of destruc-tion, its base still inclosed in the epispore is partitioned off, and the containedprotoplasm is condensed into oval corpuscles (X 320).

Figs. 4—12.—Successive stages in the development of a zygospore ;4—6, before the development of the processes (X 40); 7, 8, processesmaking their appearance from above downwards upon one of the arcuatecells (X 40); 9—11, their appearance upon the other arcuate cell simul-taneously with the increase in the size of the zygospore (9 x 120, 10 and11 X 40), in fig. 11 a slight traction has been applied to the two conjugat-ing filaments; 12, mature zygospore enveloped by the dichotomous processes,many of which are broken (x 50).

Fig. 13.— Side of attachment of an arcuate cell with processes radiatingall round (x 40).

Fig. 14.—""Vice" arrested in its development; the first process is developedin its ordinary position, but has been prolonged and developed into ordinarymycelial hyph» (X 120).

Fig. 15.—Base of a sporangiferous hypha (a) ; tb, sterile branches (cell-culture) (X 120).

Fig. 16.—Group of three small sporangia inserted with two sterile brancheson a branch (a) of the mycelial hypha (m) (cell-culture) (X 120).

Fig. 17.—Basal dilatations of lateral branches (b, b) of a mycelial hypha(cell-culture) (x 120).

Thamnidiiini elegans.Fig. 18.—Different stages of the fructification.Fig. 19.—Mycelium which has produced—(i) a large sporangium, (ii) a

dichotomy of eight small sporangia, (iii) a secondary lateral dichotomy ofmonosporic sporaugioles.

Pig. 20.—MonospwxS sporangioles with granular walls ( x 250).

Chmtostylum, Fresenii.

Fig. 21.—Lateral branch inserted, with numerous others, on the topof a bypha; it terminates in a point, and bears two false verticils of branch-lets. The lower sporangioles are of the fourth, the upper of the thirdorder (X 250).

Chatocladium Jonesii.

Fig. 22.—Fruiting hypha terminating in a point, and bearing upon amiddle dilatation monosporic sporangia with granular walls aud simple ordichotomous pedicels (X 270).

Fig. 23.—a, a monosporic sporangium, with a portion of its pedicel; 6,one ruptured by pressure, showing the inclosed smooth spore; c, c, sporesentirely freed from their sporangia; d. a spore escaping from its sporangiumat the commencement of germination (X 270).

Eigs. 24—27.—Successive stages of germination.Fig. 28.—Granular-walled balloon-like bodies terminating some of the

branches (x 270).Fig. 37.—Successive stages of fructification in cell-culture.

Chatocladium Brefeldii.

Fig. 29.—Mycelium proceeding from a single spore after sixty-sevenhours ; the lateral processes are only figured on a single branch («a).

Fig. 30.—End of a principal branch after five and a half days: a lateralprocess (c) has developed a sporangiferous branch (d), of which tlie aerialportion is shaded; it bears fertile branches (( and/"), and also sterile ones,at its base ( x 190).

Fig. 31.—Extremity of a hypha after four and a'hiili' days' culture; one ofits branches (a) is prolonged into an aerial filament, bearing laterally nu-merous groups of ripe sporangia ( x 190).

Fig. 32.—One of these groups of monosporic sporangia (x 400).Figs. 33, 34.—Lateral processes in contact with a hypha of Mucor

Mucedo(x 400).Fig. 35.—Three spores (s, s', $') which have germinated, and the hyphse of

which have fused (x 190).Fig. 36.—Two branches of a hypha which have fused, forming a loop

(x 190;.

/^JmJ&teMtfS&t.

F/G. 2.

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATES V & VI.

Illustrating Mr. Darwin's paper on the Anatomy of theSympathetic Ganglia of the Bladder in their Relation tothe Valvular System.

PLATE Y.FIGS.

1.—Posterior surface of the bladder of a young dog, stained with chlorideof gold, seen under a very low power. It shows the distribution ofnerve-trunks and ganglia in relation to large branches of blood-vessels.The blood-vessels are coloured green, the nerve-trunks and gangliaare purple.

2.—From a dog's bladder stained in chloride of gold, showing an arteryand vein with the accompanying plexus of nerve-trunks and ganglia.Hartnack, No. 4.

A,. Artery (red).A2. Vein (blue).B, B. Nerve-trunks (purple).c, c. Ganglia (purple).

PLATE VI.

FIGS.

3.—Prom the bladder of a rabbit, stained with chloride of gold, showingan artery and two ganglia. The larger ganglion fl) is surrounded bya plexus of capillaries. A nerve-trunk from each ganglion passesdown to supply the artery. Hartnack, No. 5.

• A. Artery.B, B. Nerve-trunks.c, c. Ganglia (i, and n).

a. The place where the nerve-trunks disappear in the ad -ventitia.

e f. Transverse line at which the nerve-trunk from ganglion iis supposed to be interrupted.

Bj and Bj. Nerve-trunks which ought to be continuous with eachother, and to connect the ganglia I and II together.

BD. Capillaries.4.—Nerve-trunk arising from ganglion n of fig. 3, and supplying the artery

A of the same figure. Hartnack, No. 2.A. Artery.B. Nerve-trunk.a. Nerve-fibres ending in the artery.D. Capillaries.

5.—From the bladder of a dog stained with chloride of gold. Hartnack,No. 5.

A. Artery.~&x and av Nerve-trunks arising from ganglia situated close

together on a nerve-trunk not shown in the figure.

a. Nerve-fibres ending in the adventitia.

6.—Ganglion situated on a large nerve-trunk, with smaller accessoryganglion, from the bladder of a dog stained with cliloride of gold.Hartnack, No. 5-

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATE VII,

Illustrating Ernst Haeckel's memoir on the Gastraea-Theory,the Phylogenetic Classification of the Animal Kingdom,and the Homology of Germ-Lamellae. Translated byE. Perceval Wright.

Plate VII contains a schematic section through the young stages of re-presentatives of all the different phyla of Metazoa, and will give a clear idea,not only of the homology of both primary germ-lamellse, but also of the originof the four secondary germ-lamellse. Kgs. 1—8 are schematic longitudinalsections; figs. 9—16, schematic cross sections. In all the figures theprimary inner germ-lamella (ventral lamella, entoderm, vegetative germ-lamella), including the parts derived therefrom, is indicated by the red colour;while, on the other hand, the primary outer germ-lamella (dermal lamella,exoderm, animal germ-layer) is indicated by blue. The letters are through-out the same.

a. Primitive intestine (progaster); primitive intestinal tube.b. Ventral lateral hollow muscles.c. Ccelom (body-cavity or pleuro-peritoneal cavity).d. Intestinal glandular layer (mykogastral layer).e. Dermal layer (exoderm); outer primary germ-lamella; intestinal

layer./. Fibro-intestinal layer (inogastral layer).'h. Neuro-dermal layer.*'. Gastral layer (entoderma); inner primary germ-lamella, dermal

layer.k. Germinal glands (appendages to the sexual glands).I. Skin (corium).m. Fibro-dermal layer (inodermal layer).«. Primitive brain (medullary canal).0. Primitive mouth (prostoma); primitive oral opening.r. Dorsal lateral hollow muscles.1. Dorsal intestinal vessels (aorta).«. Primitive kidneys (excretions-canal).x. Chorda dorsalis or vertebral column.2. Ventral intestinal vessel (heart).

Figs. 1—8 represent schematic longitudinal sections of gastrula fromeight diverse animal forms, i. e.—

Kg. 1.—Gastrula of Sponges (Otyntftus).!Fig. 2. „ „ Corals {Actinia).Fig. 3. „ „ Accelomi {Turbellarid).Fig. 4. „ „ I'unicata (Ascidia).Fig. 5. „ „ Molbisca (Limnceus).Fig. 6. „ „ Asterida (Urasler).Fig. 7. „ „ Crustacea (Nauplius).Fig. 8. „ „ Vertebrata (Amphioxus).

Figs. 9—16 represent schematic cross-sections through representatives ofeight different types, i. e.—

Fig. 9.—Through a simple Sponge {Otynthus) or a simple Hydro-medusa {Hydra). The wall of the primitive intestine re-mains (as in Gastrula) for life only by the two primary gerin-lamellse.

DESCRIPTION OF PLATE VII—continued.

Pig. 10.—Through a simple Acalepha (Hydroid). Between the gastrallayer (t) and the neuro-dermal layer (h) lies the fibro-dermallayer.

Fig. 11.—Through an Acceloraatous embryo {Turbellaria). The sectiongoes right through the primitive brain or cesophagealganglion (»). Between the neuro-dermal layers {h) and theintestinal glandular layers (d) are visible, moreover, the twofibrous lamella? which lie compactly on one another—theouter the fibro-dermal layer (m), and the inner the fibro-intestinal layer ( / ) .

Fig. 12.—Through an Ascidian larva, from the base of the tail, so as toput in the lowest end of the chorda (x) between the medullarycanal («) and the intestinal tube (d). Between the fibro-dermal layer (ra) and the fibro-intestinal layer (/) the coelomis visible.

Fig. 13.—Through an AmpMoxus larva (compare Kowalevsky's ' De-velopment of Amphiozus,' plate ii, fig. 20). The fibro-intestinal layer (/) is still entirely separated from thefibro-dermal layer (m); the entire body becomes barelyformed from the four secondary germ-lamellte.

Pig. 14.—Through an older Amphioxus larva. The medullary canal («)has become completely unravelled out of the horny layer (h).The fibro-dermal layer (m) is blended together with the fibro-intestinal layer (_/) in the dorsal middle line (mesentericline), and is differentiated into the skin (I) and hollowmuscles (r). Between the intestinal tube and the unravelled-out medullary canal (») is seen the commencement of the

* chorda (x).Mg. 16.—Through a worm-embryo (cephalic segment of an Annelid).

Between the dorsal (r) and ventral (b) longitudinal musclesare interposed the primitive kidneys (segmental organs, a)from the outer dermal layer throughout the body-cavity (c).On the upper side of the primitive intestine (a) is the dorsallongitudinal vessel (<), below the same the ventral longi-tudinal vessel appears (z), both enclosed in the fibro-intestinallayer ( / ) .

Mg. 16.—Through a vertebrate embryo (central section of a fish)Between the dorsal (r) and ventral (6) hollow lateral musclesis interposed the first appearance of the primitive kidneysystem («) from the skin throughout the body-cavity. On theupper surface of the primitive intestine (a) is the primordialaorta (f), below the same the outline of the heart (or thebulbus arteriosus, z) is to be seen, both enclosed in the fibro-intestinal layer ( / ) . The only real difference between thetypical transverse section of the vertebrate body and that ofthe worm-body (fig. 15) is that in the former, between themedullary tube («) and the primitive intestine (a), the chorda(x) makes its appearance.

JBNA ; 29th September, 1873.

M. IV. Vii.Y.O 0

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATE VIII,

To illustrate the Rev. O'Meara's paper on Diatom acesefrom Spitzbergen.

FIG.

1. Navicula arctica, Cleve.2. Qrammatophora arctica, Cleve; b, side view.3. Amphora lanceolata, Cleve.4. Navicula pinnularia, Cleve.5. Synedra Kamscaiica, Grun.; b, side view.6. Asterionella Cleviana, n. s., O'Meara.7. Amphora Eaioniana, n. s., O'Meara.8. Amphora Leighsmilhiana, n. s., O'Meara.9. Navicula Archeriana, n. s., O'Meara.

10. Navicula nebulosa, var.11. Synedra arctica, n. s., O'Meara.12. Navicula Auhlandica, Grun. ?

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATE IX,

Illustrating Mr. G. Busk's paper on Clavopora Hystricis—a

New Polyzoon belonging to the Family Halcyonellese.

Fig 1. Magnified view of the entire growth, (a) One of the zoocecia.

„ 2. A portion of the stem, showing the peculiar fibres.

„ 3. A portion of the capitulum, magnified to the same degree, showingone of the zoooecia containing a polypide.

.̂ 1.

\

M'FarUne 4 Enkma.LitK™

JOURNAL OF MICROSCOPICAL SCIENCE.

DESCRIPTION OF PLATES X & XI.

Illustrating Dr. Farlow's paper on an Asexual Growth from

the Prothallus of Pteris cretica.

PIGS.

1— 3.—Different forms of the prothallus of Pteris cretica, with antlieridiaand root hairs on their lower portions.

a. Scalariform duct.

I. First leaf.

r. Root.

s. Stem bud.

4.—Vertical section of prothallus somewhat less advanced than in fig. 3 ;the letters indicate the same structures as before.

5.—Prothallus producing two leaves side by side; a, scalariform ducts,b, leaf from upper, 6', leaf from under side.

6.—Longitudinal section of prothallus in fig. 1, in the direction of thearrows.

7.—Longitudinal section parallel to y in fig. 6, and more highly mag-nifled.

z. Two of the archegonium-like group of four cells, which areseen to have no immediate relation with the subjacent scala-riform ducts.

DESCRIPTION OP PLATES X & XL—continued.

8.—Transverse section of the prothallus in fig. 4 at the points; this isfigured in the plate with the under side of the prothallus uppermost.

9.—Longitudinal section of prothallus in fig. 2 in the direction of thearrows.

10.—Longitudinal secticm of a prothallus p p, similar to fig. 4, madethrough the place of origin by budding of a young plant; the otherletters as in figs. 1—3.

11.—More magnified view of a portion of the prothallus in fig. 5.

JOUENAL OF MICROSCOPICAL SCIENCE.

EXPLANATION OF PLATE XII,

Illustrating Mr. Ray Lankester's papers on " A newtype of Infusoria," and on " The Heart of Appen-

FlGS.

1—3.—Torquatella typica; three specimens, c. Capitular prominence orupper lip over-hanging the mouth.

4.—The same, a side view of another specimen, as seen swimming.

5.—The same; another specimen seen from above.

6.—Heart of young Jppendiculariafttrcata. *

7.—Heart of a full-grown specimen, s. Secondary corpuscles.8.—One heart-cell, with out-growing fibrilte; from another specimen.

i\ Secondary corpuscles.

EXPLANATION OF PLATES XIII, XIV & XIV—Continued,

list of Reference Letters—continued.ca ». Cardinal vein.mp. Muscle-plate.mp'. Early formed mass of muscles.

ov. Oviduct.p ov. Projection which becomes the ovary.10 d. Wolffian duct.

P tod. Primary points of involutiqn from the pleuro-peritpnealcavity by the coalescence of which the >Yolffian duct isformed.

su.r. Supra renal body.p n. Pineal gland.

At. Heart.v. Blood-vessel.

All the figures were drawn with the Camera Luci4a.

FIG. 1.—Section parallel with the long axis of the embryo through ablastoderm, in which the floor of the segmentation cavity (s c) is not yetcompletely lined by cells. The roof of the segmentation pavity is broken.(Magnified 60 diam.) The section is intended chiefly to illustrate the dis-tribution of nuclei (n) in the yolk under the blastoderm. One of the chiefpoints to be noticed in their distribution is the fact that they form almosta complete layer under the floor of the segmentation cavity. This probablyindicates that the cells whose nuclei they become take some share informing the layer of cells which subsequently (vide fig. 4) forms the floor ofthe cavity.

FIG. 2.—Small portion of blastoderm and subjacent yolk of an embryo atthe time of the first appearance of the medullary groove. (Magnified 300diam.)

The specimen is taken from a portion of the blastoderm which will formpart of the embryo. It shows two large nuclei of the yolk («) and the net-work in the yolk between them ; th>s network is seen to be closer aroundthe nuclei than in the intervening space. The specimen further shows thatthere are no areas representing cells around the nuclei.

FIG. 3.—Section parallel with the long axis of the embryo through ablastoderm, iu which the floor of the segmentation cavity is not yet coveredby a complete layer of cells. (Magnified 60 diam.)

It illustrates (1) the characters of the epiblast, (2) the embryonic swell-ing (e s), (3) the segmentation cavity (s c). It should have been drawnupon the same scale as fig. 4; the line above it represents its true lengthupon this scale.

FIG. 4.—Longitudinal section through a blastoderm at the time of thefirst appearance of the embryonic rim, and before the formation of the me-dullary groove. (Magnified 45 diani.)

It illustrates (1) the embryonic rim, (2) the continuity of epiblast andhypoblast at edge of this, (3) the continual differentiation of the lowerlayer cells, to form, on the one hand, the hypablast, whioh is continuous withthe epiblast, and on the other the mesoblast, between this and the epiblast;(4) the segmentation cavity, whose floor of cells is now completed-

N.B.—The cells at the embryonic end of the blastoderm have been maderather too large.

FIG. 5.—Surface view of the blastoderm shqrjily after the appearanceof the medullary groove. To show the relation pf the embryo to theblastoderm.

EXPLANATION OF PLATES XI I I , XIV & XV—Continued.

FIG. 6 a and b.—Two transverse sections of the same embryo, shortlyafter the appearance of the, medullary groove. (Magnified 96 diam.)

a. In the region of the groove. \i shows (1) the two masses of mesoblaston each side, and the deficiency of the mesoblast underneath the medullarygroove; (2) the commencement of the closing in of the alimentary canalbelow, chiefly from cells (« a) derived from the yolk.

b. Section in the region of the head where the medullary groove is de-ficient, otlier points as above.

FIG. 7 a and b.—Two transverse sections of an embryo about the age orrather younger than that represented in fig. 5. (Magnified 96 diam.)

a. Section nearer the tai l ; it shows the thickenii}g of the hypoblast toform the notochord (c#).

In b the thickening has become completely separated from the hypoblastas the notochord. In a the epiblast and hypoblast are continuous atthe edge of the section, owjng to the section passing through the embryonicrim.

F I G . 8—Surface view of a spatula-shaped embryo. The figure shows (1)the flattened head (h) where the fnedullary groove is deficient, (2) the caudallobes, with a groove between them; it also shows that at this point, themedullary groove has become roofed over and converted into a canal.

F i s . S a.—Transverse section of fig. 8, passing through the line a. (Mag-nified 90 diam.) The section shows (1) the absence of the medullary groovein the head and the medullary folds turning down at this time instead ofupwards; (2) the presence of the pleuro-peritoneal cavity in the head (p p');(3) the pompletely closed alimentary canal (a I).

F I G . 8 b.—Transverse section of fig. 8, through the line b. (Magnified90 diam.) I t shows (1) the neural canal completely formed; (2) the vertebralplates of mesoblast not yet split up into somatopleure and sphanchnopleure.

F I G . 9.—Side view of an embryo of the Torpedo, seen as a transparentobject a little older than the embryo represented in fig. 8. (Magnified 20diam.J The internal anatomy has hardly altered, with the exception of themedullary folds having closed over above the head and the whqle embryohaving become more folded off from the germ.

The two caudal lobes, and the very marked groove between them, areseen at t s. The front end of the notochord became indistinct, and Icould not see its exact termination. The epithelium of the alimentarycanal (a I) is seen closely underlying the notochord am} becoming continuous,with the epiblast at the hind end of the notochord.

The first visceral cleft (i o c) and eye (o p) are just commepcing to beformed, and the cranial flexure has just appeared.

FIG. 10.—Section through the dorsal region of an embryo somewhatolder than the one represented in fig. 9. (Magnified 96 diam.)

I t shows (1) the formation by a pinching off from the top of the alimen-tary canal of a peculiar body which underlies the notochord {%); (2) theprimitive extension of the pleuro-peritoneal cavity up to the top of thevertebral plates.

FIG. 11 a, b, and e.—Three sections closely following each other from anembryo in which three visceral clefts are present; a is the most anteriorof the three. (Magnified 96 diam.) In all of these the muscle-plates are shownat mp. They have become separated from the lateral plates in b and c, butare still continuous with them in a. The early formed mass of musclesis also shown in all the figures (m p').

The figures further show (1) the formation of the spinal nerves {sp u) as

EXPLANATION OF PLATES XIII , XIV & XV—Continued.

small bodies of cells closely applied to the upper and outer edge of theneural canal.

(2) The commencing formation of the cells which form the axialskeleton from the inner (splanchnopleuric) layer of the muscle-plate. Sec-tions b and c are given more especially to show the mode of formation ofthe oviduct (ov).

In b it is seen as a solid knob (ov), arising from the point where thesomatopleure.and splanchnopleure unite, and in c (the section behind b)of a solid rod (ov) closely applied to the epiblast, which has grown back-wards from the knob seen in b.

N.B.—In all three sections only one side is completed.

F I G . 12 a, and b.—Two transverse sections of an embryo just before theappearance of the external gills. (Magnified 96 diam.)

In a there is seen to be an involution on each side (p w d), while bis a section from the space between two involutions from the pleuro-peri-toneal cavity, so that the Wolffian duct (at first solid) (w d) is not connectedas in a with the pleuro-peritoneal cavity. The further points shown in thesections are—

1) The commencing formation of the spiral valve (a I).2) The suprarenal body (su r).3) The oviduct (ov), which lias acquired a lumen.4) The increase in length of the muscle-plates, the spinal nerves, &c.

PIG. 13.—Section through the dorsal region of an embryo in which theexternal gills are of considerable length. (Magnified 40 diam.) The chiefpoints to be noticed :

(1) The formation of the Wolffian body by outgrowths from the Wolffianduct (ted).

(2) One of still continuing connections (primitive involutions) betweenthe Wolffian duct and the pleuro-peritoneal cavity (p w d).

(3) The oviduct largely increased in size (ov).N.B.—On the left side the oviduct: has been accidentally made too small.(4) The growth downwards of the muscle-plate to form the muscles of

the abdomeu.(5) The formation of an outgrowth on each side of the mesentery (p ov),

which will become the ovary.(6) The spiral valve (a I).

Fl&. 14.—Transparent view of the head of an embryo shortly before theappearance of the external gills. (Magnified 20 diam.) The chief pointsto be noticed are—

(1) The relation of the cranial nerves to the visceral clefts and the mannerin which the glosso-pharyngeal (g I) and vagus (v g) are united.

(2) The remnants of the pleuro-peritoneal cavity in the head (p p').(3) The eye (op). The stalk, as well as the bulb of the eye, are sup-

posed to be in focus, so that the whole eye has a somewhat peculiarappearance.

JOURNAL OF MICROSCOPICAL SCIENCE.

EXPLANATION OF PLATE XVI,

I l lus t ra t ing Mr. R a y Lankes te r ' s Memoir on the Develop-ment of the Pond-sna i l .

FIG. 1.—An egg after the formation of the first cleavage groove. TwoRichtungsblasclien (J5.) are seen. Nat. size of the egg = Ti7 J inch.

PIG. 2.—An egg after division into four cleavage-masses, three of whichare seen, and the Kiehtungsblasehen (R.). Nat. size -j-j^ inch (long measure-ment).

FIG. 3.—The same quadripartite egg seen from below.

FIG. i.—An egg of a later stage in which smaller cleavage-spheres havemade their appearance at one pole. A Richtungsblaschen (JR.) is seenattached between the four larger cleavage-spheres.

FIG. 5.—The same egg seen from above.FIG. 6.—The same egg seen from below.

FIG. 7.—A later stage. At the pole g m the gastrula-invagination is nowcommencing. At It the Richtungsblaschen, entangled in the discardedvitelliiie (?) membrane, is seen.

FIGS. 8—12.—Various views of the Gastrula of Lymnaus. Naturalsize = XJTJ inch. The appearance varies according to the position whichis assumed. Fig. 9 gives a surface view as seen by reflected light. Fig.10. The same specimen seen by transmitted light. Fig. 11. Another speci-men, two thirds profile view; gm is the gastrula-mouth or orifice of invagi-nation.

FIG. 13.—The early phase of the Trochosphere with large lateral lobes (thefigure is turned sideways), m. Commencing formation of the permanentmouth. Long measurement of this specimen y |^ inch.

FIG. 14.—Trochosphere with ciliated annular ridge and commencingmouth, m. The large cells of the Gastrula-endoderm are seen to be inconnection with the body wall by means of delicate processes. Longestmeasurement of this specimen = j - ^ inch.

Fig. 15.—a, b, c, d. Successive outlines presented by such a trochosphereas that in the preceding figure during rotation in the autero-posterior direc-tion. The small prominence seen in h, and also in fig. 13, in a similar posi-tion, is probably the first indication of the foot.

JOURNAL OF MICROSCOPICAL SCIENCE.

EXPLANATION OF PLATfi

Illustrating Mr. Ray Lankester's Memoir on the Develop-ment of the Pond-snail.

Fro. 1.—An embryo between the Trochospliere and Veliger phases—sohtewhat riomp'ressed; longest diameter about -j-J-j inch. m. Mouth.v. Velum. / . Foot, g e. Gastrula-endoderm, now assuming a bilobedcharacter—the sac enclosed by it having therefore a double cavity, a rightand a left, g. Point of closure of the gastrula-mouth. p i. Pedicle of in-vagination—the future rectum, s p. The shell-patch'—a thickened area ofthe body wall, on the surface of which the shell first forms, and by iuvagi-nation of which the shell-gland is produced.

FIG. 2.—Young Veliger, surface view, showing—m. Mouth, v. Velum.f. Foot. Longest diameter about ^ j inch.

FIG. 3.—A similar specimen from the oral aspect.

I'm. 4.—A similar specimen somewhat compressed and seen in incom-plete optical section, m. Mouth. / . Foot, p i. Pedicle of invagination.* h. Shell Overlying the depression of the shell-glaud, which is now visible.

FIG. 5.—Surface view of a more advanced Veliger, longest diameterabout ^u of an inch. /. The foot, shotting bilobatioil. ft. Velum nowforming a heart-shaped area, with m, the mouth, at ita base. t. The eye-tentacles.

Fro. 6.—Surface view of a more advanced embryo, in a position fre-quently assumed at this period of development. Length of the specimen,about ^ j inch. /p. A doubtful structure, lying between the two lobesof the foot, possibly a foot-pore. Other letters as above.

K G . 7.—A Much more advanced embryo, about Jg of an inch long.fi Foot. fp. Foot-pore, v. Velum now assuming the character of " siib-tentacular lobes." t. Tentacles. I. Lung-chamber, m f. Mantle-flap,or free border of the mantle, sh. Shell.

FIG. 8.—An embryo, a little older than that Of fig. 5. Length about3*5 of an inch, compressed, treated with osmic acid, and seen in partialoptical section, m. Mouth, ph. Pharynx, ods. Odontophore-sac. f. Foot.p i. Pedicle of invagination (rectum) with crecal termination, mf. Mantle-

EXPLANATION OF PLATE XYll-mlintced.

flap-, mu. Musculapcells passing from body wall to Centrally placed gas-trula-endoderm. sh. Shell-rising up as a watch-glass, n g. Nerve-gangikm.t. Tentacle, v. Velum.

FitJ: 9.—h, 8; c. <*.—Four conditions of cells of the gastriil&erido'der'ihfrom embryos a little younger than that of Pig. 8.

Fig. 10.—A similar embryo to that of fig. 7. Letters as before.

FIG. 11.—A small embryo (about JL inch long) from a mass containingenlbrytis similar to those of figs. 7 arid 10. It is irreg'ulatly developed ahdhas the sbell-glaud occupied by a bright highly-refracting plug, is. / . Fbot.ph. Pharynx, v. Velum, mf. Mantle-flap, sh. Shell, is. Plug of theshell-gland, p i. Pedicle of invagination (rectum).

FIG. 12.—Shell-gland with plug is, and external shell ftt, of the sameembryo.

Fig. 13.—Shell-gland of another embryo and circular shell-area coveredby the disc-like shell.

FIG. 14.—Shell-gland and widely open mouth of the same from anotherembryo.

FIG. 15.—Optical section of the central portion of the shell-secreting areaat a later stage (viz. that of fig. 8), showing the last vestige of the shell-gland as a small depression.

FIG. 16.—Optical section of shell-secreting area of an embryo, similar tothat of fig. 17, showing the superficial columnar and deeper fusiform cells,and the delicate shell, sh.

FIG. 17.—An embryo younger than that, of fig. 5, considerably youngerthan that of fig. 8, compressed and treated with osmic acid. Long diameter,as thus seen, about -^ inch. / Foot. ph. Pharynx. ». Velum, ng.Nerve-ganglion, t g e. Tunic of fusiform cells covering in the gastrula.endoderm. sh. Shell, ss. Shell gland, pi. Pedicle of invagination.g s. Right-hand cavity of the bilobed gastrula-stomach. Observe thefusiform cells passing from the body-wall to be connected with this.

FIG. 18.—An embryo of nearly the same age and size as that of fig. 10,treated witli osmic acid. v. Velum. / . Bilobed foot. ph. Pharynx.n g. Nerve-ganglion, h. Heart, mf Mantle flap. «. Kidney formed asan in-pushing from the reflected flap of the mantle, m. Muscular fibresattached to the bend of the intestine, i. Intestine, g. Problematical massof cells lying close to the kidney. /. Lung-chamber, c r. Csecal termina-tion of the intestine, r m. Retractor (?) muscle.

FIG. 19.—Cells of the body-wall and gastrula-endoderm connected byprocesses of the latter, from an embryo of the same age as that of fig. 4.

FIG. 20.—Recurved and ctecal termination of the rectum developed from

EXPLANATION OF PLATE XVII.—continued.

the pedicle of invagination, from an embryo a little older than that offig. 17.

FIG. 21.—Alimentary canal of an embryo about the age of that of fig. 8.ph. Pharynx, a. (Esophagus not yet open to pharynx, st. Stomach; itsstructure concealed and obscured by the adjacent gastrula-endoderm cell-masses, i. Intestine, c. Its ctecal termination, g e. Two of the gastrula-endoderm cells, now assuming the character of pellucid globules with super-ficial granular networks, m. Branched muscular cell passing from thebody-wall to the latter. The intestine is seen to have a superficial tunic offusiform cells, and to be connected by such cells to the body-wall.

FIG. 22.—Body-wall and some of the modified gastrula-endoderm cells,from a stage between those of fig. 17 and fig. 8. ep. Epiblast. tg e. Tunicof fusiform cells covering the pellucid bodies and their granular networks,

FIG. 23.—Anterior part of the alimentary canal and body-wall, of sameage as fig. 21. ep. Epiblast. m t. Muscular tunic, m. Muscles, n g.nerve-ganglion.