210 THE DESCENT OF MAN. Part I. 



mind that long after the progenitors of the whole 

 mammalian class had ceased to be androgynous, both 

 sexes might have yielded milk and thus nourished 

 their young; and in the case of the Marsupials, that 

 both sexes might have carried their young in mar- 

 supial sacks. This will not appear utterly incredible, if 

 we reflect that the males of svno-nathous fishes receive 

 the eggs of the females in their abdominal pouches, 

 hatch them, and afterwards, as some believe, nourish 

 the young; 26 — that certain other male fishes hatch the 

 eggs within their mouths or branchial cavities ; — that 

 certain male toads take the chaplets of eggs from the 

 females and wind them round their own thighs, keep- 

 ing them there until the tadpoles are born ; — that cer- 

 tain male birds undertake the whole duty of incubation, 

 and that male pigeons, as well as the females, feed their 

 nestlings with a secretion from their crops. But the 

 above suspicion first occurred to me from the mammary 

 glands in male mammals being developed so much more 

 perfectly than the rudiments of those other accessory 

 reproductive parts, which are found in the one sex 

 though proper to the other. The mammary glands 

 and nipples, as they exist in male mammals, can indeed 

 hardly be called rudimentary ; they are simply not 

 fully developed and not functionally active. They are 

 sympathetically affected under the influence of certain 

 diseases, like the same organs in the female. At birth 

 they often secrete a few drops of milk ; and they have 



26 Mr. Lockwood believes (as quoted in ' Quart. ,Journal of Science,' 

 April, 1868, p. 269), from what he has observed of the development of 

 Hippocampus, that the walls of the abdominal pouch of the male 

 in some way afford nourishment. On male fishes hatching the ova in 

 their mouths, see a very interesting paper by Prof. Wyman, in ' Proc. 

 Boston Soc. of Nat. Hist.' Sept. 15, 1857 ; also Prof. Turner, in 'Journal 

 of Anat. and Phys.' Nov. 1, 1866, p. 78. Dr. Giinther has likewise 

 described similar cases. 



