168 TROPISMN 



late Professor Wliitman has shown by experiment that 

 this specificity is, in pigeons at least, not inherited but 

 the effect of memory images (a "conditioned reflex" in the 

 sense of Pawlow). Whitman took the eggs or young of 

 wild species, giving them to the domestic ring-dove to 

 foster, with the result, that the young reared by the ring- 

 doves ever after associated with ring-doves and tried to 

 mate with them. Passenger pigeons when reared by ring- 

 doves refuse to mate with their own species but mate with 

 the species of the foster parents. 539 This shows inciden- 

 tally that racial antagonism is not inherited but acquired. 

 We have mentioned the fact that the mating instinct 

 is determined by tropisms aroused by specific internal 

 secretions, and that in isolated male pigeons any solid 

 body can arouse the mating reaction. Craig 540 raised 

 male pigeons in isolation so that they never came in con- 

 tact with other pigeons until they were adult. One pigeon 

 was hatched in July and isolated in August. 



Throughout the autumn and early winter this bird cooed very little. 

 But about the first of February there began a remarkable development 

 of voice and social behavior. The dove was kept in a room where several 

 men were at work, and he directed his display behavior toward these 

 men just as if they belonged to his own species. Each time I put food 

 in his cage he became greatly excited, charging up and down the cage, 

 bowing-and-cooing to me, and pecking my hand whenever it came within 

 his cage. From that day until the day of his death, Jack continued to 

 react in this social manner to human beings. He would bow-and-coo to 

 me at a distance, or to my face when near the cage ; but he paid greatest 

 attention to the hand — naturally so, because it was the only part with 

 which he daily came into direct contact. He treated the hand much as 

 if it were a living bird. Not only were his own activities directed toward 

 the hand as if it were a bird, but he received treatment by the hand in 

 the same spirit. The hand could stroke him, preen his neck, even pull 

 the feathers sharply. Jack had absolutely no fear, but ran to the hand 

 to be stroked or teased, showing the joy that all doves show in the 

 attentions of their companions. 



