264 J. S. NICHOLAS 



motion is present in these objects. If such motion occurs, the 

 animal is stimulated mechanically. At times, however, these 

 animals will snap at any object with which they may come in 

 contact and engulf it with a subsequent elimination of the sub- 

 stances unfit for food. 



In addition to the observations described above, several ex- 

 periments were made using balls of filter-paper which had either 

 been previously treated with juices of beef or earthworm or had 

 been left untreated. A few experiments with sacks containing 

 test substances were also made. As the result of these tests it 

 may be said that there is a strong indication that the eyeless 

 larvae distinguish their food substances by the sense of smell and 

 mechanical stimulation. The normal animals are mainly de- 

 pendent upon sight for the final location of food. The noseless 

 larvae are dependent upon visible motion. The noseless and eye- 

 less larvae have only mechanical stimuh to guide them. 



EXPERIMENTS UPON THE ADULTS 



1. The reactions of normal animals in the light 



Reactions to motionless objects. The method used in this case 

 was the same as that used by Parker and Sheldon in their 

 experiments with Ameiurus, Mustelus, and Fundulus. 



An individual was placed in an aquarium, the sides of which 

 had been screened to obviate any distractions that might occur 

 from the presence of the observer. The aquarium was a glass- 

 enclosed one, 42 cm. in length and 26 cm. wide. This was filled 

 to a depth of 10 cm. with water. After allowing a period of 

 ten minutes for the animal to become adapted to the test aqua- 

 rium, small cheesecloth bags, equal in size and suspended at the 

 same height in the water, were introduced. These bags allowed 

 a rapid diffusion of any substances that might be contained within 

 them. The bags were hung from a rod at the top of the aquarium 

 by means of a cotton thread. The time taken for the introduc- 

 tion of the test materials was at that period at which the animal 

 had come to rest at some position near the central portion of the 

 aquarium. The bags were then introduced with as little dis- 

 turbance of the medium as possible. Because of the variation of 



