REACTIONS OF A. TIGRINUM 267 



All the experiments were positive in this series, the animal 

 showing a distinct discrimination between the test substances. 



2. Terrarium experiments 



Reactions to motionless objects. A few experiments were 

 made with the animals in a terrarium. The same substances 

 were used as in the preceding trials. The animals are almost 

 insensible to the presence of test substances, and in but one trial 

 in ten was there any indication of a detection of the difference 

 between the substances contained in the bags. This was the 

 only reaction given, all other trials giving no reaction to either 

 bag. The procedure followed was simply to place the bags near 

 each other at the bottom of the terrarium and await the reaction. 

 The one case recorded as positive showed a reaction about fifteen 

 minutes after the introduction of the materials, the animal 

 nosing the earthworm bag after passing the sand bag, and snap- 

 ping the earthworm bag. 



A comparison between the sensitivity of the adult animal in 

 the air and in the water can easily be obtained in the ordinary 

 process of feeding. Cut earthworm can be held against the nasal 

 apertures of the animal and elicit no response. If, however, the 

 animal is so situated that its nasal openings are immersed in water, 

 a very small diffusion from the forceps in which earthworms have 

 been held is sufficient to give an extremely active response. 



Reactions to moving objects. If the test sacks are moved about 

 in a terrarium in the same fashion as that described above for 

 the animals in the water, a decided reaction is obtained. In 

 many cases the animal seizes the bag with such force that it can 

 be lifted from the bottom. This is particularly true with refer- 

 ence to the earthworm bag, for the animal will quickly relinquish 

 the sand bag. It is probable that the basis of discrimination in 

 this case is one of taste. It is likely that this is the same reaction 

 as that obtained in the noseless larvae, when the sense of taste 

 or perhaps of touch, must enter into the reaction of the rejection 

 of particles unfit for food. 



