The Mammals and Man 



The metnod of rearing the young in the case of the ant-eater 

 (that of the duck-mole not being yet fully known) is that 

 the single egg is placed, as soon as it is laid, in the pouch under 

 the belly of the female. Here it hatches in a very short time, 

 and here the young animal remains for the first two or three 

 months of its life, being nourished by milk produced by the 

 mammary glands, which open into the pouch. It is certainly 

 owing to the absence of the competition of the higher mammals in 

 the regions where they are found, that these two creatures, so 

 interesting from the standpoint of Evolution, have been preserved 

 to us. 



The next group, the Marsupials, is the lowest in which we get 

 the true mammalian characteristic of the bearing of living young. 

 For while occasional members of other groups, of the reptiles 

 especially, produce live young, the actual state of affairs is funda- 

 mentally different. In these latter the egg is merely retained in 

 the genital duct until the young creature emerges. It is merely 

 hatched inside the body of the mother instead of outside. But 

 in the Marsupials the developing young receive nourishment from 

 the mother, during prenatal life, other than what is contained 

 in the yolk. This nourishment is obtained in the form of a 

 secretion from the wall of the uterus, there being as yet (with a 

 single partial exception) no real connection between mother and 

 young. 



The peculiar method of nourishing and protecting the young 

 Marsupial after birth is of course well known. The young are 

 born in a very immature and helpless condition, and are placed 

 by the mother in her pouch. The mouth becomes permanently 

 attached to the nipple of the dam, and the young creature re- 

 mains thus for a considerable time, the milk being pumped into 

 it by the mammary gland rather than sucked in by the efforts 

 of the creature itself. 



The Marsupials are further characterised by the possession 

 of an extra pair of bones in the pelvis, which function as sup- 

 ports for the pouch ; by the peculiar and primitive arrangement 



of the reproductive organs ; by their still poorly developed brain ; 

 i 129 



