REACTIONS OF A. TIGRINUM 259 



NORMAL BEHAVIOR 



The larvae are in almost incessant motion under laboratory- 

 conditions, swimming about the aquaria apparently in a con- 

 stant search for food. Only after they have become gorged 

 with food will they sink to the bottom, and even then they are 

 seldom motionless, but continue to move about by combined 

 walking and swimming movements, stopping to examine any 

 object that attracts their attention. 



The adults used in this work had lived under laboratory con- 

 ditions for three months previous to the time of the experimental 

 work. The movements of the adult animals are ordinarily not 

 particularly rapid, but the application of stimuli causes a re- 

 markable acceleration of reaction. If placed in an aquarium 

 provided with a float and left undisturbed, the animals will 

 generally be found perfectly motionless upon the float, or else 

 partly submerged with the head protruding above the surface. 

 When placed in an aquarium filled with water to a depth of 

 6 or 7 inches, but without a float, the animals are restless for a 

 time after their introduction, due probably to the handling which 

 they have received. They soon come to rest, however, with only 

 an occasional sluggish movement. The animals were admirable 

 for the experimental conditions imposed. They can be handled 

 singly and show no trace of the educative process which is said 

 to occur in some forms, viz., Ameiurus, after having been sub- 

 jected to trials of this nature. An attempt was made to obtain 

 evidence of any difference in reaction which might occur in this 

 way by taking the speed of the reaction as an indicator. The 

 last control experiments, with the conditions as nearly as possible 

 like the original experiment, showed an average time slightly 

 longer than the original. 



During the process of acclimatization, the animals were fed 

 solely upon small pieces of earthworm. The degree of visual 

 sensibility is high. In many cases the animals will secure the 

 earthworm while it is sinking to the bottom of the aquarium. 

 If the food has come to rest, the animals often take great interest 

 in the observer, and for this reason the walls of the aquarium 



