392 Inland Water Culture 



water-fleas have consisted in the main of the counting 

 of individuals in random catches; and, as Haeckel ('90) 

 long ago pointed out, this has about as much economic 

 value as the counting of straws would have in an oat 

 field. 



The extraordinary growths of certain plancton algae 

 (Anabaena, Aphanizomenon, etc.) that often give 

 trouble in water-supply reservoirs, might be made into 

 fish food through the agency of daphnias, if we only 

 had learned how to manage our water crops. 



FIG. 235. Gammarus fasciatus (after Paulmier). 



Water-fleas are of very great value as food for young 

 fishes, they form also a considerable part of the food 

 of such larger fishes as are equipped with gill strainers 

 for gathering them out of the water. They are, of 

 course, largely absent from the water during the winter 

 season. Their value as forage organisms lies in their 

 good quality and their extraordinary reproductive 

 capacity. 



The scuds This group of herbivores is typified by 

 Gammarus (fig. 235) a hardy, wide-ranging habitant of 

 the water weeds. It swims well, yet prefers to occupy 

 the sheltering crevices of dense leafage. It can leap 



