PLAY AND INSTINCT. 63 



The complexity of instinct that is often so baffling, 

 and its wonderful adaptiveness are, after all, not more 

 difficult to explain than the other things about an organ- 

 ism. For example: " The marvellous instinct that leads 

 the wood bee (Xylocopa violacea Fabr.) to build its in- 

 tricate nest in the trunks of trees is not more inexplicable 

 than the faceted eyes of these very insects. . . . The 

 principles involved in the morphological structure of 

 the organ also account for the instincts; and there are 

 also to be taken into account homology, analogy, and 

 parallel development, individual variation, natural selec- 

 tion, and the resulting adaptation, cross-breeding, and 

 atavism; here also there are cases of rudimentary and 

 hindered development, natural or artificial deformity." 

 No part can be had, in the genesis of instinct, by associa- 

 tion resting on a foundation of previous experience, what 

 we mean by understanding, intelligence in its widest 

 sense; nor by acquired tracts, for these are not hereditary. 



After giving this elaboration of Ziegler's theory in 

 his own terms, I make these essential points: 



1. The assumption that intelligent acts are the 

 ground of the origin of instinct is unwarrantable. Even 

 if the Lamarckian theory is not absolutely tabled, it is 

 much wiser, so long as the question remains open, to be 

 content with the leading Darwinian principle, since its 

 grounds are more assured. 



2. In the explanation of instinct (and of play) we 

 need consider only natural selection, for we do not know 

 any other principle of development. The simple reflex 

 action must develop in the process of time into the com- 

 plex reflex actions that we call instinctive. In this way 

 we try to explain their adaptability as well as we explain 

 organic adaptability in general. Whether it can be satis- 

 factorily done is another question. I am not one of the 



