02 THE PLAY OF ANIMALS. 



the address already cited, with the exception of one 

 point, which I shall indicate at once. Ziegler has set 

 forth with great skill, clearness, and technical scholar- 

 ship a point of view which is now more and more 

 attracting the attention of modern zoologists; and the 

 leading features of his exposition coincide with the 

 views of many modern psychologists. In all instinct 

 there is a close connection between a particular stimulus 

 and a particular act, a connection that is of utility 

 under ordinary conditions. Is this useful adjustment 

 attributable to conscious will? No. On the contrary, 

 the idea of consciousness must be rigidly excluded from 

 any definition of instinct that is to be of practical 

 utility. (Who can tell whether a dog, a lizard, a fish, 

 a beetle, a snake, or an earthworm performs an action 

 consciously or unconsciously? It is always hazardous in 

 scientific investigation to allow a hypothesis which can 

 not be tested empirically.) 



It follows, that such fixed and useful connections 

 between stimulus and action are to be treated as reflexes. 

 Instincts are, as Herbert Spencer has rightly said, com- 

 plex reflex acts. But the connection between reflex 

 action and instinct is explicable only by means of selec- 

 tion, and selection in the Weismannian sense, which 

 excludes the inheritance of acquired characters. " In 

 the progress of phylogenetic development natural selec- 

 tion lays the foundation of instincts, and accordingly 

 they are useful. Instincts are adapted to conditions, and 

 serve generally for the preservation of the individual, 

 always for that of the species." There must be, physio- 

 logically speaking, certain connecting paths among the 

 ganglion cells that — existing as hereditary predisposi- 

 tions — contain " hereditary tracts." 



* See James, The Principles of Psychology, ii, p. 391. 



