CONSCIOUSNESS IN EVOLUTION. 401 



in the struggle for existence. So they were doubtless compelled 

 to assume an arboreal life, which required little or no modifica- 

 tion of the limbs for its maintenance, although the ultimate pro- 

 duction of the grasping thumb from their primitive squirrel-like 

 feet may be traced to this mode of life. The acquisition of a 

 hand must be regarded as the first step in that marvelous acces- 

 sion of experiences which is the condition of mental development. 

 And this latter growth has taken the place of all other means of 

 conquering a position in the world of life, so that man has even 

 retrograded in the efficiency of bodily powers. He has lost the 

 prehensile quality of the hind feet, and the special usefulness of 

 his canine teeth. But the competition among men continues to 

 be such as to render it in the highest degree improbable that he- 

 will, as a species, lose the position gained, or suffer anyj^rolonged 

 diminution of the power of intelligence. 



Now it is obvious that the more restricted the conditions of the 

 life of a given animal type, the more sensitive it will be to changes. 

 Hence it is that the risks to the existence of Carnivora, Artiodac- 

 tyla, Prolosciclia, etc., are much greater than to the omnivorous, 

 all-adaptive order of Quadrumana. The same is true of mind. 

 The greater the proportion of unconscious automatism of habits, 

 the less the power of adaptation ; and this must be the condition 

 of all animals whose structure is so specialized as to place them 

 beyond reach of competition, or to cut them off from a wide range 

 of experiences. The greater the degree of consciousness of stim- 

 ulus, the greater will be the degree of adaptability to new rela- 

 tions, and to such constant rousing the unspecialized mind is 

 always open. If, without strong natural weaj^ons, vigilance is the 

 price of existence ; if not confined by organization to a j^eculiar 

 kind of food, ceaseless investigation is stimulated. And these are 

 the mental peculiarities which distinguish the monkeys among all 

 the Mammalia. 



The reverse of this picture may now be described, as has been 

 done by Prof. Vogt. It is well known that the young of many 

 parasitic animals are free and active, and discover during migra- 

 tion the localities to which they afterward attach themselves for 

 life. During the early stages they present the characteristic marks 

 of their order and class, and in some instances the males, remain- 

 ing free, continue to do so. Such are the Entoconcha miraMlis, 

 the Sacculmce and the Trematoda ; the first a mollusk, the second 

 a cirrhijied crustacean, the third a worm. On their becoming at- 

 26 



