S&O THE DESCENT OF MAN 



of some species, for instance of Theridion Uneaium, it would 

 appear that these sexual characters of the males have not 

 as yet become well fixed. Canestrini draws the same con- 

 clusion from the fact that the males of certain species present 

 two forms, differing from each other in the size and length 

 of their jaws; and this reminds us of the above cases of 

 dimorphic crustaceans. 



The male is generally much smaller than the female, 

 sometimes to an extraordinary degree," and he is forced 

 to be extremely cautious in making his advances, as the 

 female often carries her coyness to a dangerous pitch. 

 De Geer saw a male that "in the midst of his preparatory 

 caresses was seized by the object of his attentions, enveloped 

 by her in a web, and then devoured, a sight which, as he 

 adds, filled him with horror and indignation." *' The Rev. 

 O. P. Cambridge" accounts in the following manner for 

 the extreme smallness of the male in the genus Nephila: 

 "M. Vinson gives a graphic account of the agile way in 

 which the diminutive male escapes from the ferocity of the 

 female, by gliding about and playing hide-and-seek over 

 her body and along her gigantic limbs; in such a pursuit 

 it is evident that the chances of escape would be in favor 

 of the smallest males, while the larger ones would fall early 

 victims; thus gradually a diminutive race of males would 

 be selected, until at last they would dwindle to the smallest 

 possible size compatible with the exercise of tneir generative 

 functions — in fact, probably to the size we now see them, 

 i.e., so small as to be a sort of parasite upon the female, and 

 either beneath her notice or too agile and too small for her 

 to catch without great difficulty. " 



Westring has made the interesting discovery that the 



"• Aug. Vinson ("Araneidea des lies de la Eeunion," pi. vi. figs, 1 and 2) 

 gives a good instance of the small size of the male in Epeira nigra. In this 

 species, as I may add, the male is testaceous and the female black, with legs 

 banded with red. Other even more striking cases of inequality in size between 

 the sexes have been recorded ("Quarterly Journal of Science," 1868, July, 

 p. 429); but I have not seen the original accounts. 



" Kirby and Spence, "Introduction to Entomology," vol. L, 1818, p. 28a 



« "Proc. Zoolog. Soc," isn, p. 621. 



