626 JONATHAN RISSER 



2. Experiments 



To ascertain whether any stimulus other than the optic is 

 called into play in the finding and taking of food the following 

 experiments were performed. 



Toad No. 1 was placed in the box, which was empty except 

 for a covering of moist filter paper on the floor, and allowed 

 to remain undisturbed for some time. There was no excited 

 hopping about during this period of illumination. The light 

 having been cut off, the toad crept along the wall, and finally 

 came to rest in a corner where it attempted to burrow as though 

 it were on soil. After two hours of darkness some mealworm 

 larvae were introduced into the box. These were placed centrall}^ 

 on the floor and as these changes were made in darkness the 

 larvae were not seen by the toad. The toad was then lifted 

 from its position in the corner of the box and placed imme- 

 diately over the glass plate on which the larvae were and facing 

 them. In this position there was no thigmotactic stimulation, 

 as there would have been in the corner position. By listening 

 to the sounds within the box the movements of the toad could 

 be followed. The position of the larvae and the toad were 

 noted at the end of two minutes of darkness. The toad had 

 resumed the corner position, the larvae had moved out and away 

 from the plate, one of them being within 2 inches of the toad. 

 Two minutes of darkness brought no further movement on 

 the part of the toad. The larvae were distributed around 

 the sides of the box. After another minute of darkness, the 

 light was turned on and at the first visible movement of the 

 mealworms, the toad turned and jumped toward them. There 

 followed no movements on the part of the toad in successive 

 periods of darkness; but each time the box was illuminated the 

 least movement on the part of the mealworms called forth char- 

 acteristic movements from the toad. 



Toad No. 2 was tried wdth dungworms in a manner similar 

 to that just described for Toad No. 1. No notice was paid to 

 the worms in the dark but in the light the toad followed the 



