48 MINOR ABNORMALITIES— HERMAPHRODITISM 



symmetrical instance recorded by Stewart {235) from the mackerel, the two testes lay dorsally to 

 the ovaries. Judging from the figures, all four glands opened posteriorly into a single efferent duct. 



(4) In the Salmonidae hermaphroditism appears to be exceedingly rare. Its occurrence is 

 mentioned by Simpson (Todd's Cyclopaedia of Anatomy and Physiology, London 1836-9, II. p. 697), 

 but otherwise the only example I have come across is that described by Stewart (235) from 

 preserved material in the trout. This case merits separate mention, on account of the differ- 

 ences occurring normally between the sexes in the Salmonidae, and also because, on other grounds, 

 it presents features of very great interest. The right genital gland is ovarian in structure. The 

 left, which is the larger, consists chiefly of ovary, but has a middle portion with the structure of a 

 testis. There are two genital ducts, one on either side, leading from the posterior ends of the gonads 

 to the uro-genital chamber. The specimen was therefore regarded as being a fundamentally male fish 

 possessing also partly the female character. The previous history bore out that on two occasions 

 ripe eggs had been extruded from its belly by artificial pressure, and these eggs, although kept 

 completely isolated, developed normal young. 



At the time of examination several ova were lodged in the right duct close to its termination 

 in the uro-genital chamber. A short distance in front of this point the duct in question was 

 ruptured or defective. There were between two or three dozen loose ova in the body cavity, but 

 these had apparently escaped from a rupture of the right ovary or from the opening in the wall of 

 the right duct alluded to above. 



Nothing in the description indicates the presence of oviducal pores leading from the body cavity 

 into the uro-genital chamber, and presumably in this case the ova dehisced into the interior of the 

 gland and not into the body cavity. 



The frequency with which hermaphroditism appears in fishes, normally or abnormally, and the 

 fact that the Ascidia are hermaphrodite, have been taken as evidence that the chordate ancestor was 

 monoecious (Haeckel, Howes, Masterman and others). It does not appear that the conclusion is 

 necessary on either ground, any more than that the alternation of generations found in many widely 

 different animals is due to common ancestry, or that the hermaphroditism of the Cirripedes 

 indicates a primitive monoecious condition in the crustacean stock. I believe that here we 

 have an instance (see p. 5) in which a certain "potentiality" (i.e. hermaphroditism on the one 

 hand or unisexuality on the other) has become fixed as normal in certain forms (e.g. hermaphroditism 

 in Ascidia, Myxine, Serranus, etc. ; unisexuality in Amphioxus and most fishes), while in these forms 

 the converse potentiality still manifests itself in a sporadic and " teratological " manner, through 

 some inherent variation tendency the persistence and strength of which are independent of atavism. 



This view, while not directly supporting Pilseneer's l position that the hermaphroditic is always 

 derived from the unisexual condition, points to a property inherent in animal life whereby either 

 state may conceivably receive the opportunity of gradually replacing the converse one through 

 the ordinary working of natural selection. 



II. 



SHORTENING AND CURVATURE OF THE SNOUT. 

 (Pug-head ; Bulldog-head, etc.) 



References : 



Salmonidae. — Carlet 36; Couch £5 ; Day 54. II. p. 102; Lidth de Jeude 114; Lowne 

 146 p. 55; Malloch 147a; Saint Hilaire 213 I. pp. 283-287; Stoddart 239; Tornier 250; 

 v. Krauss 134- 



Specimens have been sent to the author by Henry Lamond, Esq. (Salmo fario), and Peter 

 M'Nair, Esq. (Salmo salar). As regards early stages, Girdwoyn 81 fig. 112, illustrates a trout 

 embryo with shortened upper jaw and defective also as regards the eyes. A somewhat similar 

 specimen is figured by de Quatrefages (19S, PL VII. Fig. 2). 



1 "Hermaphroditism in Mollusea," Q.J. Microsc. Society, London, 37 (19-46). 



