8o EVIDENCES AND LIMITATIONS 



simpler organisms. This supposition is confirmed by 

 the evidence bearing upon the comparative antiquity 

 of species which has been obtained by other Hnes of 

 investigation. 



4. Another argument for the natural evolution of 

 species is derived from embryology, or the study of 

 immature and unborn offspring. A remarkable sim- 

 ilarity is found in their manner of development in 

 different species of the same general group. The 

 similarity is most complete in the earliest stages, so 

 complete indeed that, prior to a certain stage of devel- 

 opment, the embryos of the different species are indis- 

 tinguishable from each other. It is also noticed that 

 the higher organisms to an observable extent recapitu- 

 late in their embryonic growth the phases of develop- 

 ment of their several species which the evolutionary 

 theory hypothecates. These phenomena are most 

 readily interpreted and accounted for from the evolu- 

 tionary standpoint. The parallehsm between the 

 growth of individual organisms and the development 

 of species is not indeed complete, but this is easily 

 accounted for by the supposition that the variations 

 which result in the divergence of species may to some 

 extent modify the embryonic stage of growth. The 

 more or less defective but recognizable resume of earlier 

 natural history which is still discoverable seems to declare 

 an ancient pedigree, and a common ancestry for the 

 species which are thus shown to be mutually related. 



5. Somewhat connected with this argument is the 

 inference made from the presence of rudimentary and 



