124 ISABEL M CRACKEN. 



Wheeler refers to as " latent heredity." ^ " The vestigial instinc- 

 tive action," says Wheeler, "presents itself as an act of racial or 

 phyletic recollection and must, like the representations of indi- 

 vidual memory, depend on psychological dispositions abiding in 

 latency, just as the visibly morphological characters of the adult 

 organism arise from the visibly physiological dispositions in the 

 germ plasm. These dispositions must be inherited with great 

 tenacity and persistency, since vestiges, both instinctive and 

 structural, often remain latent for generations and then suddenly 

 manifest themselves under stress of extraordinary stimuli." 



In the case at hand, the "extraordinary stimuli," whatever 

 these may be, that produce the manifestation are not external. 

 The movement has every appearance of being " spontaneous," 

 the release of "internal energy." The behavior here noted is 

 strikingly parallel to that noted by Jennings with reference to 

 lower organisms, " Often, perhaps usually in lower organisms," 

 observes Jennings, " movement in a certain direction is due only 

 to the release of inhibition. The organism moves in a given 

 direction because it is moving from internal impulse, and because 

 movement in this direction is not prevented." ^ Jennings observes, 

 further, that "the behavior of the lower organism at any moment 

 depends upon its physiological state at that moment," 



Flight in the silkworm, manifesting itself as it does, without 

 external stimulus and when the activities of the mating reflexes 

 are suspended, is apparently a spontaneous movement dependent 

 conceivably upon the physiological condition of the insect for the 

 time being, and involves the awakening of a latent instinct. 



In the presence of the female, the whole attention of the insect 

 is monopolized for the time being with the impetus to mate, 

 This " state " supercedes every other possible state and prompts 

 or guides the insect to one line of conduct only. The action 

 which is the normal consequent of this state is mating ; all other 

 possible actions are suppressed, and under normal conditions, as 

 stated, habitually suppressed. The manifestation of the flight 

 function under these experimental conditions shows that, though 



1 Wheeler, "Vestigial Instincts in Insects and other Animals," Amer. Jour, of 

 Psychol., Vol. XIX., pp. 1-13. 



2 Jennings, "Behavior of Lower Organisms," p. 284. 



