Emhryological Evidences 207 



went hand in hand with other differentiations, because of 

 which we distinguish " higher " forms of hfe from " lower." 

 There is the arrangement of the hairs on the arms of man. 

 These hairs, whatever " use " we may ascribe to them, run 

 in a direction for which no 

 explanation has yet been 

 suggested on the theory 

 that these structures, like 

 all the others of the living 

 thing, have meaning in the 

 sense of fitness or adapta- 

 tion to the interests or wel- 

 fare of the individual or 



the species (Fig. 53). OnVC^V 



m 



the other hand, the assump- 1 1 1 /. ^1 

 tion that at some remote 

 past man's mode of life was ^ 

 different from that of the 

 man whom we know offers 

 a reasonable explanation. 



Emhryological Evidences 



We have learned to 

 take for granted individual 

 variation among familiar 

 persons. As large num- 

 bers of individuals and 

 fetuses are compared, we 

 find that every part of 

 every individual shows such 

 variation at every stage of 



Man Male Chimpanzee 



Fig. 53. Hair Tracts on the Arms 



The curious arrangement of the hairs on the 

 arms of anthropoids — from the wrist and 

 from the shoulder toward the elbow — sug- 

 gests an adaptive value among tree dwellers. A 

 similar arrangement in man is not so easily- 

 explained. After Romanes. 



growth. Now, a compari- 

 son of adults with infants and fetuses, in respect to variability 

 of parts, shows that structures which deviate little among 

 adults have varied little in the course of development, and they 

 have varied little from the ancestral conditions. This means 



