I20 Journal of Comparative Neurology. 



a tendency to pursue, but as a rule these seem to be due to 

 vague amatory instincts which develop before their distinctive 

 criteria. Careful observation will be useful along the lines here 

 suggested. Closely correlated with this phase is the combative 

 play of nearly all animals. This is of two kinds and the distinc- 

 tions must be carefully drawn to make observations of any value. 

 The playful butting and kicking of herbivora and the nagging of 

 other animals in the same litter can be traced to inherited in- 

 stincts of competitive strife with others of the same sex. Often 

 the early simulation very soon graduates into the reality, as in 

 cockerels of the same yard, while in other cases the sedateness 

 of maturity obliterates the play, which reappears in reality with 

 the annual occasion therefor. The other class consists of imita- 

 tions of conflict with competitors of other species or powerful 

 prey. The kitten which crouches behind a bush and rushes out 

 with great bounds upon its mate who is creeping toward it and 

 then rolls over in vigorous thoYight velvet struggles to overpower 

 it experiences something of the joy of battle which will glorify 

 the real war with rat or gopher. Where parent and progeny 

 thus play, as do the bears especially, there is also the (uncon- 

 scious ?) element of instruction involved. 



Social instincts greatly modify the play impulse and, of 

 course, these vary with the gregarious or solitary habits of the 

 animal in question. In solitary or monogamous animals the 

 social play is confined to the young of the same litter, though 

 when circumstances being unrelated animals intimately together 

 they may learn to play among themselves. In gregavious 

 animals the young play promiscuously for a time. In animals 

 which form communities the communal nature soon becomes 

 characteristic of the play. Troops of lambs follow the adventur- 

 ous leader until such time as parental anxiety or other influences 

 cause them to fly tumultuously back to their mothers. 



One of the early instincts of a social sort is a compound of 

 acquisitiveness and rivalry. The young of many animals go 

 through the motions of hiding articles before they have definite 

 judgements as to the service of the hiding, indeed the instinct 

 often remains throughout life much more prominent than neces- 

 sary to the regime of the individual. 



As bearing on the acquisitive habits of mammals the follow^ 



