THE PHYLOGENESIS OF VERTEBRATES 41 



however, are very simply constructed in these particulars 

 and remain close to the lower type as shown in the marsupials. 

 Primates are also primitive in their muscular system, pos- 

 sessing in many instances a single undifferentiated muscle- 

 mass where the members of other Orders show a complex 

 group of muscular units. 



Aside from the adaptation of their extremities to an ar- 

 boreal life, the one line of development by which the Primates 

 have become differentiated is in that of their central nervous 

 system, and especially that of the cerebrum, which has given 

 them a far greater capacity for recording their sensory im- 

 pressions, and thus of profiting by experience, the basis for the 

 development of reason. It is chiefly in this respect that the 

 human species has developed so far beyond the condition of 

 the other Primates that the world has long, and perhaps will- 

 ingly, been deceived in regard to their true relationship. In 

 spite of all prejudice, however, man is, anatomically speak- 

 ing, a typical primate, closely related, even in many of the 

 smaller details, to the rest, and the only way in which he has 

 proved superior, through the excessive development of the 

 cerebral hemispheres, is not a modification calculated to pro- 

 duce important correlated changes in the other parts. Of 

 the two living Sub-orders, the Lemur oidea and the Anthro- 

 poidea, the former are the more primitive and more nearly 

 represent the generalized Mesodonta from which the race 

 sprung. In the completeness of the partition which separates 

 the orbital and temporal fossae, Man 'is seen to be an Anthro- 

 poid; and in important characters, such as the reduction of 

 the premolars from three to two, he agrees with the Catarrhine 

 division of this Sub-order. If we employ the usual schedule 

 of values to be attached to points of structural difference, as 

 used for the purpose of classification, we cannot fairly place 

 him in a Family apart from the large tailless apes of the Old 

 World, and aside from this we have several intermediate 

 links, which the researches of the past few years have brought 

 to light, and which reduce even the slight gap formerly con- 

 sidered to be between them. 



