THE BRAIN IN THE EDENTATA. 393 



of the brain becomes a necessity if the individual is to siu'vive. But after the brain has 

 attained to a certain degree of development, and competition becomes keener, endless 

 varieties of special modifications take place in different mammals in adaptation to special 

 kinds of life. Tliose animals whose brains do not keep pace with the general advancement 

 of the Class must either drop out of the race or adopt some special protective mechanism 

 or habit of life which may save them from extinction. The Insectivora, which are the 

 specialized remnants of one of the lowliest stages of mammalian development, are examples 

 of this. The more generalized mammals continvie their onward progress in virtue of their 

 cerebral superiority, but from time to time groups branch off and, forsaking the fierce 

 race for pallial supremacy, adojit habits of life and corresponding bodily modifications 

 which will enable them to maintain the struggle against those of their relatives whose 

 better brain-endowment enables them to endure without any marked bodily specialization 

 for self-defence. But the individual which devotes all its energies to self-defence at the 

 expense of its brain is bound before long to share the fate of tlie GUjptodon, even though 

 it be " built like Eome," as the late W. K. Parker remarked. 



The last descendants of tbe main generalized stem which never turned aside to 

 adopt protective modifications or specialized habits of life, but prevailed in virtue of 

 their brain-superiority, became the Primates. They have attained the loftiest position in 

 the mammalian series, and at the same time retained much of the simplicity of the 

 generalized type from which they sprang. It seems as though the adoption of specializa- 

 tions of an offensive or defensive nature is a confession of weakness. 



The Ungulate lagged behind in the race for supremacy in cerebral organization at an 

 early period, and by fleetness of limb and largeness of body has sought to compensate for 

 its inferiority of brain. But in spite of this fact it still leads an open life, and the 

 progressive development of its brain is still of vital importance. Hence we find that 

 in the various offshoots fi'om the primitive Condylartlira the growth and elaboration 

 of the brain become conditions of survival. In all probability Orycteropus became 

 specialized from the generalized type at about the same time as the Ungulata, and it 

 is not improbable that it may even have branched off from the primitive Ungulate stock. 

 The generalized type of its body and limbs shows that it must have adopted its pro- 

 tective habits of life at this period, and the configiu'ation of its brain indicates that it 

 may for some time have followed the Ungulate line of development. Innumerable 

 modifications of the generalized type branched off at the same time as the ancestors of 

 the Ungulata, and, either from lack of the capacity to develop their brain or to adopt 

 some manner of protection, they succumbed in the struggle and became extinct. Of 

 the few types which svirvived this process of extinction, Ilanis is probably an 

 example. Although its brain has reached a very considerable degree of development, 

 it has survived by virtue of its peculiar protective mechanism and of its naode of life. 

 Soon after the branching-off of the Ungulata, it is probable that the Rodentia became 

 specialized as a distinct group. They may have arisen from tlie common stem from which 

 also the Carnivora and probably the Xenarthra sprang, but if so they branched off 

 from this stem before the close of the Eocene, and by adopting a safe mode of life and 



SECOND SERIES. — ZOOLOGY, VOL. VII. 54 



