14 G. C. Embody. 



largely of finely divided plant remains. They would always resort to 

 this method of concealment when disturbed. 



They were often greatly excited when bits of freshly killed Asellus 

 or Planorbis were thrown into the water and in a few minutes 

 nearly all would collect about the food. — At such a time they showed 

 a pugnacity equal to that of their parents and very similar to that 

 observed by Andrews (1907) in the case of the young of Astacus 

 leniusculus in the third larval stage. Often several young would 

 seize the same piece with their mandibles and this would be followed 

 by a vigorous use of all of the thoracic appendages, and a violent 

 "kicking" of abdomens which usually tore the food particle into as 

 many shreads as there were amphipods. Each one carrying a choice 

 morsel would subsequently swim away to a dark corner. 



The young amphipods at first found the food thus administred 

 quite by accident. The final reactions, however, were undoubtly in- 

 fluenced by the sense of smell or taste, or perhaps both. Fluids given 

 off from the food gradually diffused through the water to a short 

 distance in all directions. Any amphipod coming into this region in- 

 stantly changed its behavior. Ordinarily a young amphipod swims in 

 a straight or a somewhat curved path using its pleopods only. However 

 when one enters the region polluted with fluids from the food, it 

 quickly, becomes very erratic both in its course and in its movements. 

 It now jumps first in one direction and then in another by flexing 

 and reflexing its abdomen, and at the same time moving the antennae 

 in wide sweeps. Whenever it touches unpolluted water it immediately 

 turns back. This may continue for a number of seconds or perhaps 

 a minute but the general movement of the animal is gradually towards 

 the food which it eventually touches. One jump and the particle is 

 grasped by the gnathopods and appendages of the mouth while the 

 peraepods and abdomen continue to move vigorously. If the piece of 

 food be not large the young amphipods will Hkely carry it away 

 bodily. 



The young of E. gracilis are smaller than those of the preceding 

 species and unlike them are incapable of swimming more than a few 

 millimeters without becoming exhausted. During the first day they 

 exhibit no incUnation to feed or to climb and but a slight desire to 

 conceal themselves under bottom debris. In the course of a few days 

 however, they have gradually acquired all the activities of the young 

 of G. limnaeus although these activities are never so marked as they 

 are in the latter species. 



