Brooks.] 198 [November 17, 



the latter attains its full size, becomes sexually mature, and dis- 

 charges its spermatic fluid into the water to gain access to the eggs 

 carried by other immature chains. 



The fact that impregnation takes place, not, as we might expect, 

 within the body of the solitary, but within that of the chain salpa, is 

 no objection to this view, for the number of animals whose eggs are 

 fertilized within the body of the female is quite small, and in at least 

 one genus, Hippocampus, the eggs are received into a specialized 

 brood sack in the male, and are there impregnated. 



We can also find analogy for the singular fact that the eggs always 

 develop females, while the males are formed by budding. The fer- 

 tilized eggs of the bee always give rise to females, while the males 

 are developed by the virgin bee, through what seems, as pointed out 

 by Prof. McCrady, to be most properly regarded as a process of in- 

 ternal gemmation; and we cannot fail to mark the very striking par- 

 allelism between the process of reproduction as manifested in Salpa 

 and the bee. 



The fertilization of the eggs within the bodies of "zooids" produced 

 by budding from the body of that whose ovary gave rise to the eggs 

 is not unusual among the Tunicata. The u zooids" of most of the Tu- 

 nicata are hermaphrodite, and develop eggs of their own, but, at 

 least in the case of Pyrosoma, Perophora, Didemnium and Amauric- 

 ium, the egg which undergoes impregnation and development within 

 the body of the "zooid " is derived, not from its own ovary, but from 

 that of the generation before, and the eggs produced in the body of 

 the second generation must pass into the bodies of the "zooids" of the 

 third generation before they can be fertilized. The essential differ- 

 ence between this process and that presented by Salpa, is that in 

 Salpa the sexes are distinct, and as the chain salpa has no ovary the 

 process of budding stops with the second generation; while as the 

 " zooids " of the other Tunicata are hermaphrodite the process may 

 go on indefinitely. 



The history of Salpa is of especial interest, as it throws a great 

 deal of light upon the manner in which separation of the sexes may 

 be brought about in forms which were originally hermaphrodite, and 

 it is also interesting to note that the elasoblast, the history of the de- 

 velopment of which shows it to be the homologue in the female of 

 the testicle of the male, is concerned in reproduction, although it has 

 lost all the characterstics of a sexual organ, and is simply a supply of 

 food. 



