OUR EMBRYONIC DEVELOPMENT. 71 



a brilliant light on the corresponding stages of our 

 ancestral tree, in accordance with the great law of 

 biogeny. But even the cenogenetic phenomena of 

 adaptation, the formation of the temporary foetal 

 organs — the characteristic foetal membranes, and 

 especially the placenta — gives us sufficiently definite 

 indications of our close genetic relationship with the 

 primates. 



