HOMO LOGY. 91 



to have read of anything similar among other 

 dwarf tribes. 



To account for the presence of rudimentary 

 mammse, and their occasional development in 

 the male, Darwin suggests that the ancestors of 

 the mammalia may have possessed lacteal 

 glands in both sexes, which afterwards became 

 aborted in the males, being no longer required, 

 perhaps in consequence of the females becoming 

 less fertile.* But this case is perfectly ana- 

 logous to that of the presence of marsupial 

 bones, and sometimes of a rudimentary pouch 

 in the males of marsupial animals ; and if 

 Darwin's explanation was correct, we might 

 reasonably expect to '* find at least some species 

 of mammals with fully developed mammas, and 

 some marsupials with a fully developed pouch 

 in both sexes. f It appears more probable 

 that the structure of one sex (and both sexes, 

 as we have seen, exist potentially in the germ) 



* Descent of Man, vol. i. p. 209211. 



t In the pipe-fishes the males alone are usually provided with a 

 marsupial sac, the walls of which are supposed to secrete a nutritious 

 fluid. Darwin, op. cit. vol. ii. pp. 21, 22. In Alytes and some other Ba- 

 trackia, it is the male who takes charge of the eggs which are laid by 

 the female, and carries them about, attached to his own body, till they 

 arc hatched. 



