72 



THE EVOLUTION OF SEX. 



great majority of the cirripedes are hermaphrodite; but among the 

 barnacles proper — the stalked forms, which are nearer the ancestral 

 type — - separate sexes sometimes occur. On the females of a few of 

 these, pigmy males, like those found upon hermaphrodites, also occur. 

 These pigmy males, whether on females or hermaphrodites, are not 

 only dwarfish, but are very often degenerate, sometimes wanting 

 (according to Darwin) both alimentary canal and thoracic legs. Some 

 of them, in fat, are little more than parasitic testes. 



Fig. 17. — Myzostomata: A hermaphrodite (1), and a 

 pigmy male (2). — From Nansen. 



(1) The original state of affairs in this case was probably the 

 ordinary crustacean condition of separate sexes. (2) The males, as 

 in some of the " water- fleas " or copepods, tend to be smaller, — 

 smaller, indeed, to a vanishing-point, — while the females became 

 more and more sluggish, and settled down. (3) In the genera Alcippe 

 and Cryptophialus y in the species Ibla cummingii and Scalpellum 

 ornatum, we find true females, with attached pigmy males, often 

 several, leading a shabby existence as parasites. (4) In other species 

 of Scalpellum and Ibla the same pigmy males occur, but attached, as 



