ENTOMOSTRACA AND PHYLL6pODA. 26 1 



times before it begins to resemble its motlier, a simi- 

 lar peculiarity being noticeable in many of the Ento- 

 mostraca. 



These little crustaceans are found in almost every 

 body of still water. Some prefer the surface, where, 

 on a sunshiny day, they are occasionally seen in im- 

 mense numbers, sinking when a cloud shades them, 

 and rising again to the sunlight. Others are to be 

 taken only in deep water, while still others can be ob- 

 tained only at night. Many however, are collected in 

 every gathering of aquatic plants. They abound at 

 all seasons of the year, even in midwinter. Their 

 movements are rapid and characteristic. An -Ento- 

 mostracan may be readily recognized as such by the' 

 unaided sight, on account of the peculiar leaping, or 

 short, jerking motions with which it travels through 

 the water. 



They are not only interesting little creatures to the 

 microscopist, but they are exceedingly useful as well. 

 They play an important part in the food-supply of 

 fishes,, forming the chief article of diet for some of our 

 best fresh-water fishes. And they are almost as im- 

 portant as scavengers. Their favorite food is dead 

 and decaying Algae and animal matter, which, if 

 allowed to remain in the great abundance in which it 

 often exists, our ponds and slow streams would before 

 long become putrid and unbearable. But these nu- 

 merous little creatures, by eating this refuse matter, 

 transform it into an innocent and innocuous material, 

 and confer a benefit both on themselves and on us. 

 Prof. C. L. Herrick, writing on this subject, says, 

 "Their importance depends largely on their minute 

 size and unparalleled numbers. The majority of non- 



