4 G. C. Embody. 



the water gave a temperature above 16" C. They were equally abun- 

 dant in rapid and quiet water; in fact, in any place where there was 

 sufficient accumulation of Chara, water cresses and dead leaves, and 

 where the water was suffiently cool. 



Hyalella knickerbockeri and Eucrangonyx gracilis are not 

 so hmited in distribution as the foregoing forms. Both are found in 

 the cold waters of the trout brook and in the warmest waters of Ren- 

 wick Marsh. They occur in Cayuga Lake, and in Fall Creek and the 

 Inlet above and below the falls wherever there is an accumulation of 

 living or dead vegetation. In spite of the drying up of the marsh, the 

 burning of the cattails and sedges and the freezing of the ground to a 

 depth of from six to ten inches, both amphipods appear each spring in 

 the usual large numbers in various marsh pools. 



IV. Food. 



So far as could be determined the food taken by individuals of 

 the four species did not differ in quality. That which was offered to 

 aquarium specimens, if accepted or refused by one was treated in 

 exactly the same manner by members of the other three species. In 

 general amphipods feed largely upon plants either living or dead and 

 upon carcasses of animals in which putrefaction has not progressed too 

 far. Dead leaves and plant stalks are readily stripped of their softer 

 tissues and these constituted the larger portion of the food of the am- 

 phipods under observation. 



One large female G. fasciatus living in a small aquarium was 

 observed repeatedly pulling of a dying leaf of an aquatic moss and 

 later swimming about the aquarium carrying it until the leaf had been 

 eaten. In this case there was a deliberate selection of one dying leaf 

 from a multitude of living ones. 



On the sides of a few of the aquaria there appeared large growths 

 of the alga, Coleochaete. The smaller amphipods discovered these 

 very soon after they had appeared and immediately began to eat out 

 the central cells. It was not uncommon to see seven or eight amphi- 

 pods in each aquarium perched upon as many different plants gree- 

 dily eating away the cells. Eventually the animals cleaned the sides 

 of the aquaria nearly as effectively as might have been done by 

 snails. 



Among the aquatic plants largely eaten by amphipods, the follo- 

 wing were noticed: The epidermis of leaves and stems of Elodea, 

 Myriophyllum, Utricularia, Chara, Sphagnum and Lemna; the 



