POPULAR SCIENCE 



17 



assumed to have begun with an opposable great toe and to 

 have ended in the distinctive human great toe, which is the 

 corner-stone of the foot. It is possible, however, that the 

 opposabihty of the simian great toe may be a secondary 

 character, and that the common ancestor may have had a 

 clasping foot. 



Pocock proceeds to discuss the monkey hand, foot, and 

 method of locomotion in the trees and on the ground, and 

 points out the fundamental differences between these and the 

 corresponding organs and functions of the gibbon. He con- 

 cludes that the arboreal and terrestrial habits have been learnt 



A. Foot of the bipedal arboreal lemur. 



B. Foot. of the quadrupedal arboreal monkey 



•C. Foot of the gorilla, a bipedal, partly arboreal ape 

 J!)» Foot of man. 



Fig, I. 



independently by the monkeys and the apes ; that " since 

 ancestral traits lost in the adult often persist for a longer or 

 shorter time during youth, we may conclude that the orang's 

 progenitor was biped before the adjustment of the organisation 

 for climbing had reached the pitch exhibited by the existing 

 ape " ; and that the short broad foot of the chimpanzee and 

 gorilla, " their ability to stand and walk erect, and their peculiar 

 way of climbing, all point to the conclusion that they are 

 descended not from a truly arboreal ape, but from an ape 

 which had already taken to terrestrial life." If the specialised 

 monkey foot may thus be ruled out as a stage in the ancestry 

 of man, the question arises, What evidence is there as to the 

 condition of the great toe in the primitive primate ? 



At the sixth week the human embryo has the fan-shaped 



