REACTIONS OF A. TIGRINUM 279 



with irritating substances. The presence of substances such 

 as ammonia or oil of cloves will cause a motor reaction in A. 

 tigrinum as a reflex of skin irritation. 



The results of the present series might be summed up as 

 follows. Normal animals will discriminate between test sub- 

 stances and react positively toward the substance giAdng an 

 olfactory stimulus, whether that substance is moving or motion- 

 less, and whether the animal is under conditions of light or 

 of darkness. 



Animals deprived of the olfactory sense by occluding the nasal 

 passages show the same reaction to both test substances and react 

 more quickly to moving substances than do the normal animals. 

 There is no olfactory discrimination. 



Animals which have been blinded respond to olfactory stimulus. 

 If a moving object does not give rise to olfactory stimulation, the 

 animal moves about in an indefinite manner without a definite 

 objective, but will locate and try to obtain a mo\'ing focus 

 giving an olfactory stimulus. 



Animals which have been blinded and nose-stopped give no 

 reactions except to moving objects and show no discrimination 

 between test substances. 



Normal animals give no reactions to normal substances carried 

 in odor streams. They will, however, give motor reactions to 

 irritating substances. 



SUMMARY 



1. General observations upon the growth and behavior of 

 operated larvae show that the visual sense is the primary sense 

 used in obtaining food. 



2. When motionless food substances are the only ones present, 

 the olfactory apparatus functions to a greater extent in eyeless 

 larvae than it does in normal animals. 



3. The experiments upon adult animals (table 1) indicate 

 that, while the eye is the most important agent in obtaining 

 food, yet with the nose alone the animals are capable of detect- 

 ing and locating definite food substances. 



