EVOLUTION THE MASTER-KEY 



to man, and the present opinion appears to give 

 the preference, on the whole, to the chimpanzee; 

 while agreeing with the general conclusion of Dar- 

 win that man, the gorilla, and the chimpanzee 

 are derived from a common ancestor now extinct. 

 This ancestor may perhaps have more nearly re- 

 sembled the gibbon than any other existing form. 



The older evidence for man's relation to the 

 anthropoid apes is familiar to all. He resembles 

 them in physical structure to an almost incredi- 

 ble degree. He shares with the chimpanzee and 

 the gorilla some three hundred structural features 

 which are not even possessed by any of the lowest 

 order of monkeys. 1 His earlier stages of develop- 

 ment are quite indistinguishable from those of the 

 anthropoid apes, about the embryology of which 

 very little was known in the early days of evolu- 

 tion. But recently there have been discovered 

 two noteworthy facts which are of theoretical in- 

 terest and may prove to be of great practical 

 importance. 



In the first place, it has recently been found that 

 there is a whole series of diseases which are common 

 to man and the anthropoid apes, but which attack 

 no lower animal. For long these were thought to 

 be peculiar to man alone, but Metchnikoff and 

 his fellow-workers at the Pasteur Institute have 

 shown that certain of them can be communicated 

 to the anthropoid ape, and that protective or cura- 



1 See Nature, March 9, 1905, p. 434. 

 136 



