THE EVOLUTION OF MAN 



nipples certain indications which perceptibly 

 point toward their original location in a pocket, 

 a sure sign that the ancestors of all of them once 

 went through the marsupial stage. A very good 

 proof is furnished' by the present living mar- 

 supials in their peculiar formation of that im- 

 portant organ of propagation in the mother's 

 womb, which we mentioned once before, the 

 placenta. While in our previous remarks we 

 mentioned only the different forms of this 

 placenta, we now notice that the marsupials 

 seem to have remained stationary at the point 

 where the placenta was in its first stage of de- 

 velopment. 



The majority of the marsupials have no 

 placenta at all, and this is an indication of a 

 former and still more ancient condition which is 

 closely connected with the existence of a pocket 

 and the premature birth of the young. The 

 young was born so early and required the use 

 of the milk-nipples so prematurely that it did not 

 at all need a placenta connected with the nourish- 

 ing juices of its mother's blood. On the other 

 hand, a few species of Australian marsupials, the 

 Perameles, show the beginning of a very simple 

 and rudimentary placenta, and thus furnish an 

 additional proof that this important organ went 



74 



