THE LOGIC OF EVOLUnON 75 



plasmic nerve-centers and glands. But birds have a still 

 higher temperature. 



We have already seen that the development of the neuro- 

 muscular system, the lengthening of the embryonic period and 

 accompanying increase in size of the eggs have greatly 

 diminished their number and made the care of eggs and young 

 of an importance which cannot be overestimated. The bird 

 deposits its eggs in a nest ; in all but the very lowest mammals 

 the mother carries them in her body. 



The period of gestation and infancy is continually lengthen- 

 ing and the strain on the female increases correspondingly.^ 

 Something pointing toward or approaching family life ap- 

 pears far down in the history of placental mammals. The 

 chief instincts and the dawning intelligence seem to center 

 around the young. The plays of lower mammals educate 

 both mother and offspring. 



The earliest of even the placental mammals were apparently 

 comparatively stupid. But care of young and the continual 

 harrying by their reptilian overlords was a school of severe 

 but steady and sure training. Says Lull of the '' archaic " 

 mammals: " Their brain was singularly old-fashioned, gen- 

 erally small, but always relatively undeveloped in comparison 

 with that of modernized mammals of equivalent bulk, espe- 

 cially in the part wherein the intelligence lay. Hence it is 

 not surprising that the career of these forms was brief and 

 that with rare exceptions they have suffered racial death and 

 vanished as utterly as did the dinosaurs before them." ^ 



Brain and intelligence are rising to leadership in the neuro- 

 muscular partnership. The dominance of muscular bulk, ar- 

 rangement and power, even of weapons of offence or defence, 

 is beginning to pass away. Everything points toward a new 

 and thorough revolution. All our " modernized " mammals 

 possess some or considerable intelligence and learn by expe- 

 rience. They are educable. 



2 H. 549. 



