2S8 THE DOCTRINE OF DESCENT. 



discoidal placenta, or that the accordance is based on 

 consanguinity with the discoido-placental mammals. We 

 have already (p. 272) objected to the inference that all 

 mammalian orders are akin, should be drawn with cer- 

 tainty from the superficial accordance of the placenta, 

 and we must therefore justify ourselves now, when we 

 lay a stress on the accordance of the placenta of man 

 and ap.es. The orders mentioned above all possess a 

 placenta of small extent and discoidal form. In the 

 shape of this disc, and in the number and distribution 

 of the blood-vessels in the umbilical cord by which the 

 foetal respiration and nutrition are carried on, sundry 

 varieties occur. Thus in the family of the Pithecoid 

 apes, the placenta falls into two discs, whereas the 

 umbilical cord agrees with that of man ; in the American 

 apes, on the contrary, the placenta is simple and the 

 blood-vessels are different. In the orang and gorilla we 

 know nothing of these organs, but the chimpanzee agrees 

 with man, in that it has a simple discoidal placenta 

 with two conducting (arteriae umbilicales) and one re- 

 conducting vessel (vena umbilicalis). 



With a general similarity of the human placenta with 

 that of the discoido-placental mammals, man is specifi- 

 cally nearer to one at least of the so-called Anthropoid 

 apes, than this one is to the other apes. And thus the 

 constitution of the placenta is certainly of great impor- 

 tance in discriminating the systematic position of man. 

 Enormously improbable as is the chance contemplated 

 above, equally probable and solely credible is con- 

 sanguinity ; and with regard to general organization, in 

 any specific comparison of man with the mammalia, the 

 apes must occupy the foreground. 



