52 Ol^GANIC EVOLUTION — rilYSICAL 



in their ontogenies the evolution of their respective 

 races, develop along parallel lines up to the point at 

 which the races diverged, after which they develop 

 along lines whicli are no longer parallel. It follows 

 that the nearer the relationship between any two 

 species, the longer does the course of the development 

 from germ to adult proceed along parallel lines. Mr. 

 Herbert Spencer puts the matter very clearly. 



" The germ out of which a human being is evolved 

 differs in no visible respect from the germ out of which 

 every animal and plant is evolved. The first conspicu- 

 ous structural change undergone by the human germ, 

 is one characterizing the germs of animals only — differ- 

 entiates tliem from the germs of j^lants. The next 

 distinction ostablislied is a distinction exhibited by all 

 Vcrtelmda ; but never exhibited by Annulosa, Mol- 

 lusca, or Codcntcrata. Instead of continuing to resemble, 

 as it now does, the rudiments of all fishes, reptiles, 

 birds, and mammals ; tlie rudiment of man assumes a 

 structure that is seen only in the rudiments of mammals. 

 Later, the embryo undergoes changes which exclude it 

 from the group of implacental mammals; and prove 

 that it belongs to the group of placental mammals. 

 Later still, it gi'ows unlike the embryos of those placen- 

 tal mammals distinguished as Tingulato or hoofed ; and 

 continues to resemble the unguiculate or clawed. By 

 and by, it ceases to be like any foetuses but those of 

 the quadrumana ; and eventually the foetuses of only 

 the higher quadrumana are simulated. Lastly, at birth, 

 the infant, belonging to whichever human race it may 

 do, is structiirally very much like the infant of all 

 human races ; and only afterwards acquires those various 

 minor peculiarities of form that distinguish the variety 

 of man to which it belongs." — Principles of Biology, vol. 

 i. p. 142. 



Following the above train of thought it may be 

 remarked, that any trait which appears late in the 



