BULLETIN OF THE UNITED STATES FISH COMMISSION. 211 



of spermatozoa already alluded to also have a tendency to be bent to- 

 wards the outlet of the tubules, giving rise to a fringe-like appearance 

 on either side of follicle with a clearer space between the edges of the 

 fringe-like masses of spermatozoa. In fact it is plainly to be seen that 

 the spermatozoa are being budded off from the spermatogenetic layer, 

 and that the appearances just described are a result of that process. It 

 results from this that the structural peculiarities of the testicular tu 

 bules are very characteristic, so that once recognized they will never 

 afterwards be confounded with the arrangement observed in the ovary 

 of the female, where, as in the hermaphrodite species, the ova may be 

 seen in different stages of development, though where the majority of 

 the ovules have attained nearly full development, it may happen that 

 few of the nascent ovules closely adherent to the walls of the follicles 

 are visible. 



The distinction between Ostrea edulis and the American and Portu- 

 guese species is therefore very marked and important. Mobius, Der 

 Auster und die Austernwirthschaft, Berlin, 1877, page 19, says of their 

 species : " Oysters are hermaphrodites. In thelargest number of indi- 

 viduals, in the whole reproductive organ, I found only spermatozoa, 

 but no eggs. In seven oysters which carried blue brood in the beard, 

 the sexual gland contained only spermatozoa. Three oysters with 

 younger white embryos in the beard had no spermatozoa in the sexual 

 gland. In the most of the brood-bearing oysters the sexual gland con- 

 tained neither eggs nor spermatozoa. Of 309 oysters, which were 

 taken, on the 25th May, from four different banks east of the island of 

 Sylt and afterward examined from May 26 to June 1, 18 per cent, 

 were hermaphroditic, and of the remaining 82 per cent, one-half were 

 egg-bearing, the other half sperm- bearing. In none were the sexual 

 products completely mature. From these observations I conclude that 

 the eggs and spermatozoa do not develop simultaneously but success- 

 ively in the sexual gland ; that spermatozoa may be developed very 

 soon after the discharge of the ova, and that probably one-half of the 

 oysters of one locality during a breeding period produce only eggs, and 

 the other half produce only spermatozoa." To the same effect are the 

 statements of Lacaze-Duthiers ; but Davaine seems to have first no- 

 ticed the peculiar aggregations of spermatozoa in oval masses in Ostrea 

 edulis. Brooks thinks " Gerbe's statement, that among 435 European 

 oysters one year old he found 35 with young, 127 with ripe eggs, and 

 189 with ripe semen, seems to be sufficient to show the incorrectness 

 of Lacaze-Duthiers' conjecture that the functionally male condition pre- 

 cedes the functionally female condition." 



This is about the state of the controversy at present in regard to the 

 breeding habits of Ostrea edulis. The only authority, as far as I am 

 aware, who distinctly takes the ground that eggs of this species are 

 fertilized in the reproductive organs is Horst, who says : " Not only do 

 ine embryos pass through their first stages of development within the 



