REACTIONS OF A. TIGRINUM 265 



the conditions under which experimentation took place, the 

 •stimulus caused by the introduction of the test sacks is negligible. 

 One of the bags was filled with minced earthworm and was 

 weighted with sand, while the other bag contained sand alone. 

 Ten trials were made in each series, the three animals being 

 tested in turn with at least a thirty-minute interval between 

 trials. 



Under normal conditions, the adult Amblystoma moves slowly 

 about the aquarium seeking for a projection upon which it can 

 rest, preferably upon the surface of the water. Under condi- 

 tions of stimulation the animal becomes restless, hastening 

 its ordinary movements and proceeding with a greater degree 

 of rapidity about the aquarium. It is this increase in activity 

 that is spoken of in the following series as the 'beginning reaction.' 

 All reactions in this series were considered to be consummated 

 when the testing material was seized by the animal. 



The conditions under which each animal was tested were con- 

 stant in regard to the motion of the test substances. The 

 other factors, however, such as the distance of the test substance 

 from the animal, the distance of the test substances from each 

 other, and the position of the test substances with reference to 

 the animal were considered. The variations in the conditions 

 preclude any factor that might arise in connection with the above. 



The response to the stimulus was, in every case, a positive one. 

 Differentiation between the test substances was always in favor 

 of that sack containing the food material. In order to show a 

 few of the experiments and the variations imposed as well as the 

 procedure, two of the individual cases are given below. 



Trial 4. Animal A. Placed in aquarium at 11.05. Animal 

 is restless. Test sacks introduced at 11.20. The animal moves 

 restlessly about sides of aquarium, moving to center of the 

 aquarium where the sacks are suspended within 2 inches of each 

 other, noses earthworm bag, circles sand bag, goes to earthworm 

 bag, noses, snaps, and seizes. Reaction is completed in two 

 minutes. 



Trial 7. Animal A. Placed in aquarium at 3.10. Test sacks 

 introduced 3.15. The animal swims about, passes sand bag, 



