210 
THE DESCENT OP 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 svngnathous 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 
2,1 Mr. Lockwood believes (as quoted in ‘ Quart. Journal of Science.’ 
April, 1868, p. 269), from what he lias observed of the development of 
Hippocampus, that the walls of the abdominal pouch of the male 
in some way afford nourishment. On male Jishes hatching the ova W 
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, 1806, p. 78. Dr. Gunther has likewise 
described similar cases. 
