EVOLUTIONS OF ORGANIZATION. 29 



circumstances of geological change been most active 

 since then, and passed from piscine forms on to 

 man. And neither the structure nor the intellect 

 of man surpasses now the perfection that it had 

 reached in ancient Egypt and in Greece ; though 

 the lapse of time has proved sufficient for varia- 

 tions and degenerations. The definite lines of 

 development on which the head had gradually 

 risen to the perfection exhibited by the classic 

 sculptors are incapable of being cafried further: 

 the face is curved in under the skull so far that 

 it could not be carried back to a greater extent, 

 and leave room for teeth, tongue, and throat. 



Nor can attention be too frequently directed to the 

 ordered and completed evolution seen in the history 

 of the heart, a remarkable series from the simple to 

 the complex, but showing in the amphibian and 

 reptilian stage a more complex mechanism, yet less 

 perfect machine than in the fishes, so that, as I have 

 elsewhere said, "it might have been difficult to 

 explain if it could have been noted by an observer 

 before birds and mammals appeared on the earth." 1 

 But the mechanism gradually developed is com- 

 pleted, with variety, in the bird and mammal, 

 and shows no sign of undergoing further com 

 plication. 



1 Animal Physiology, p. 116. 



