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 carried further: 

 the face is curved m 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. 



