338 BULLETIN OF THE 



ruals the males are developed through a process which falls short of 

 perfect sexual reproductiou, and are therefore lower than the female, 

 as far as their origin is concerned, with the well-known fact that 

 throughout the animal kingdom cases occur in which the male is to a 

 greater or less degi«ee supplemental to, and more or less degraded in 

 accordance with the degree to which it is subsidiary to the female. 



The supplemental males of certain cirrhipeds, the male Argonaut, 

 with its parasitic hectocotylus arm, and the small males carried upon 

 the backs of certain female spiders are well-known instances of the 

 existence of such a relationship between the sexes. I am not pre- 

 pared at present to connect these two sets of facts in any way, but we 

 can hardly avoid the conclusion that there is a real connection be- 

 tween them, and that one may furnish the means for explaining the 

 other. 



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, 

 : .s not unusual among the Tunicata. 



As already mentioned, this was first observed in Pyrosoma by Hux- 

 ley, and has since been seen in Didemnium, Perophora, Amauricium, 

 Botryllus, and Salpa, and there is good reason for believing that it 

 will be found to occur in most tunicates. The zooids of these tuni- 

 cates are hermaphrodite, and develop eggs of their own, which, how- 

 ever, must pass into the bodies of the zooids of the next generation 

 before they can be impregnated, and the ova which are formed in the 

 ovaries of this generation must pass into the bodies of the third, and 

 so on. 



The essential difference between this process and that in Salpa, a 

 difference which is here pointed out for the first time, is, that since 

 the sexes are here distinct, the chain-salpa contains no ovary, and 

 the process therefore comes to an end, while the zooids of the other 

 tunicates are hermaphrodite, and the process may therefore go on 

 indefinitely. 



The way in which close interbreeding is prevented in these Tunicata 

 is worthy of notice, and shows that in cases where this would seem 

 likely to occur special arrangements may exist to render it impossible. 

 In most hermaphrodite animals self-fertilization is prevented by the 

 existence of a difference in the periods at which the two reproductive 

 elements ripen. In the hermaphrodite Tunicata just mentioned, self- 



