332 HENRY b. ward: 



surface waters. In the former eyes were present to be sure, but 

 the pigment was much reduced. According to Garbini (96) 

 subterranean forms present these same differences in color from 

 individuals of the species found at the surface but are further 

 distinguished by diminutive size and weakness. Only two 

 species were found which were characteristically subterranean. 

 Lauterborn (94a) notes that much the same species are present 

 on Heligoland in a dark closed well as in an open light one. 

 The fauna was here very scanty. Here also Lorenzi (98). 

 Packard (94) and Lendenfeld (96) have given summaries of 

 omr knowledge regarding cave animals with frequent references 

 both morphological and ecological to the freshwater fauna of 

 such localities. The observations of Garbini (96) were made 

 largely on material from water-pipes. Whipple (98a) has made 

 similar studies in Massachusetts. Hero also Yin'-. 



Though numerous experimental researches have been made on 

 the ability of animals to become acclimatized to higher temper- 

 atures, there have been few observations on the forms which 

 occur under similar conditions in thermal springs. Both 

 Bruner (95) and Kellicott (97a) record species collected from 

 boiling springs, but without more precise data concerning con- 

 ditions. 



The importance of the plankton as fish food was pointed out 

 byZacharias (93a) and Fric and Vavra (94) and discussed in 

 detail in connection with the food relations of the water by 

 I and Ward (95). Here also Field (97). 



Walter (95) demonstrated by statistics the proportional re- 

 lation in fish ponds between the amount of plankton and the 

 growth of the young fish. Kochs | 92 i found that Entomostraca 

 could be enormously multiplied by the use of fertilizers in the 

 p, and Zachi 97) reports that the fertilization of fish 



ponds doubles the amount of plankton present. Variations in 

 the fertility of different water basins call for more precise 

 investigation and for the selection of suitable areas for inten- 

 sive aquaculture as in agriculture. Here also Hofer (96). 



[stvanffy (94) shows that the diatoms are an important 

 source of food supply to the young fish, but that the species of 



