THREE STAGES IN DEVELOPMENT. 36 1 



embryos of the lower and the higher Vertebrates ; as yet, 

 however, the embryo of Man is hardly distinguishable from 

 that of the higher Mammals^ Finally, in the third stage 

 (lower row of Section III.), in which the gill-arches have 

 already disappeared and the face is formed, the differences 

 become more evident, and grow, henceforth, more and more 

 strikino;. The sie'nilicance of such facts as these cannot be 

 over- estimate d.-^^^ 



If there exists an inner, causal connection between the 

 incidents of germ-history and those of tribe-history, as in 

 accordance with the law of heredity, we must assume then 

 these ontogenetic facts immediately afford most important 

 phylogenetic conclusions. For the wonderful and compre- 

 hensive harmony between the individual evolution of Man 

 and that of other Vertebrates is only explicable by assuming 

 the descent of these from a common parent-form. Indeed 

 this common descent is now granted by all able naturalists, 

 who in place of a supernatural creation assume a non- 

 miraculous evolution of organisms. 



