OLFACTORY REACTIONS IN AMPHIBIANS 641 



The totals of the trials carried on with the larva of the first 

 set gave these results: In 160 trials, food packet was found 120 

 times. Trials carried on from time to time up to the accidental 

 loss of the tadpoles resulted in similar ratios. 



6. Second set of tadpoles. The conditions were unfavorable for 

 keeping these tadpoles and because of this circumstance only a 

 small number of individuals were available. The trials were 

 carried out in a manner similar to those for the first set. 



It needs only be said that the results were similar to those 

 obtained from the experiments of the first set. Precautions 

 were taken with this set to have the two packets identical in 

 appearance, and to transpose them in position. To avoid the 

 accidental finding of the packets as much as possible, they were 

 placed some distance from the sides of the vessel. The toad 

 tadpoles swam more rapidly than the frog tadpoles, and were 

 also more erratic in their movement in the water. It could be 

 easily determined whether they were influenced by the presence 

 of the food mass near them. In a few cases only did there seem to 

 be a visual stimulus influenchig the tadpoles to react; such being 

 occasioned by the very lively actions of other tadpoles ah'eady 

 at work on the food mass. 



c. Third set of tadpoles. For the purpose of verifying the 

 results of the previous experiments, similar experiments were 

 performed with the tadpoles of the third set in June and July 

 of the third season. As stated, these tadpoles were obtained 

 from two different localities and kept successfully in the labora- 

 tory, metamorphosis being deferred for the time being. The tad- 

 poles were unquestionably those of Bufo americanus, having; 

 been obtained earlier than the time when the mating call of 

 Fowler's toad was heard. 



The food used in these experiments was dead and partly 

 decomposed frog tadpoles, earthworms, and beef liver. These 

 materials were either placed freely in the vessel or covered with 

 cheesecloth one or two layers in thickness. In a similar way, as 

 previously described, two packets were used in some of the 

 trials; one containing the food, the other being identical in appear- 

 ance but without food. 



