NOTE ON A HERMAPHRODITE TROUT

G. R. DE BEER

Fellow of Merton College, Osford

ONE FIGURE

In the course of his experiments with trout, Mr. Huxley came across a hermaphrodite specimen, the histological study of which he very kindly entrusted to me. The trout was 60 mm. long, and had a normal testis on one side and an ovotestis on the other. A section through this structure

is reproduced in the accompanying photograph. For the greater part of its length this gonad was a normal testis (as comparison with testes of normal fish revealed), but at the cranial extremity it consisted entirely of female tissue with oocytes. The photograph shows the transitional zone, the two kinds of tissue being in intimate association. Mrsic ('23), who has made a detailed study of the effects of late fertilization in trout, has observed that not only do gonads change from a female to a male condition, but that they may also at a certain stage of development do the opposite. If in an otherwise male gonad the germ cells cease increasing in number and increase in size, an ovary

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is obtained. Conversely, in a female gonad, increase in the number of the cells instead of growth will give rise to a testis (loc.cit., p. 181).

Mrsic found that in seven of his trout raised from eggs fertilized twenty-one days late, intersexual stages were present. The gonads were female at their cranial end and male posteriorly, and the change appeared to be taking place from female to male in a caudocranial direction. This is what is probably taking place in this specimen, but it is to be noted that it was not late fertilized, but fertilized at the normal time. Other examples of spontaneous hermaphro- dites are to be found in the frogs described by Witschi ( '14), and Crew ( '21).

LITERATURE CITED

CREW, I?. A. 1921 Jour. Genetics, vol. 11. MRSIC, W. 1923 Arch Ent. Mech., Bd. 98. WITSCHI, E. 1914 Arch. mikr. Anat., Bd. 85.