THE SEXES, AND CRITICISM OE SEXUAL SELECTION, i 7 



very diminutive are forced to task their agility to the utmost in making 

 advances to their unamiable mates. So again, crustacean males are 

 often smaller than the females; and in many parasitic species what 

 have been well called ' ' pigmy ' ' males illustrate the contrast in an 

 almost ludicrous degree. 



Fig. 8.— Male (c), Worker (/>), and Queen (a) Ant 

 From Chambers's Encyc, after Lubbock. 



Two cases from aberrant worm-types exhibit very vividly this same 

 antithesis of size. Among the common rotifers, the males are almost 

 always very different from the females, and much smaller. Sometimes 

 they seem to have dwindled out of existence altogether, for only the 

 females are known. In other cases, 

 though present, they entirely fail to 

 accomplish their proper function of 

 fertilization, and, as parthenogenesis 

 obtains, are not only minute, but 

 useless. In a curious green marine 

 worm, Bonellia, the male remains 

 like a remote ancestor of the female. 

 It lives parasitically on or within the 

 latter, and is microscopic in size, 

 measuring in fact only about one 

 hundredth part of the length of its 

 host and mate. Somewhat similar 

 to the case of Bonellia is that of a 

 viviparous coccus insect {Lecaniam 

 hesperiduni), where the males are 

 very degenerate, small, blind, and 

 wingless. In spite of this condition, we should indeed think because 

 of it, they are very male; for even the larvae, while still within the 

 mother, have been shown to contain fully developed spermatozoa. 



Fig. 9. — Relative sizes of a male and a female 

 Rotifer (Hydaiina senta). — From Leunis. 



