Chap. VI. Affinities and Genealogy. 163 



It may bo suggested, as another view, that long after the 

 progenitors of the whole mammalian class had ceased to be 

 androgynous, both sexes yielded milk, and thus nourished their 

 young; and in the case of the Marsupials, that both sexes carried 

 their young in marsupial sacks. This will not appear altogether 

 improbable, if we reflect that the males of existing syngnathous 

 fishes receive the eggs of the females in their abdominal pouches, 

 hatch them, and afterwards, as some believe, nourish the 

 young ; 30 — 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, keeping them there until the tadpoles are- 

 born; — that certain 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 

 suggestion first occurred to me from the mammary glands of 

 male mammals being so much more perfectly developed than 

 the rudiments of the 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 merely not 

 tally developed, and not functionally active. They are sympa- 

 thetically affected under the influence of certain diseases, like 

 the same organs in the female. They often secrete a few drops 

 of milk at birth and at puberty : this latter fact occurred in the 

 curious case, before referred to, ■where a young man possessed 

 two pairs of mammaB. In man and some other male mammals 

 these organs have been known occasionally to become so well 

 developed during maturity as to yield a fair supply of milk. 

 Now if we suppose that during a former prolonged period male 

 mammals aided the females in nursing their offspring, 31 and that 

 afterwards from some cause (as from the production of a smaller 

 number of young) the males ceased to give this aid, disuse of the 

 organs during maturity would lead to their becoming inactive ; 

 and from two well-known principles of inheritance, this state of 

 inactivity would probably be transmitted to the males at the 

 corresponding age of maturity. But at an earlier age these 



30 Mr. Lockwood believes (as by Prof. Wyman, in ' Proc. Boston 

 quoted in 'Quart. Journal of Science,' Soc. of Nat. Hist.' Sept. 15, 1857; 

 April, 1868, p. 269), from what he also Prof. Turner, in ' Journal of 

 lias observed of the development of Anat. and Phys.' Nov. 1, 1866, p. 

 Hippocampus, that the walls of the 78. Dr. Giinther has likewise de- 

 abdominal pouch of the male in scribed similar cases. 

 6ome way afford nourishment. On 31 Madlle. C. Eoyer has suggested 

 male fishes hatching the ova in their a similar view in her ' Orisine <U 

 mouths, see a very interesting paper l'Homme,' &c, 1870. 



