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Cincinnati Society of Natural History. 



the lakes are so shallow. The largest lake— a salt lake near 

 Lincoln — is one or two miles long and one-half broad, but 

 its deepest parts are said to be less than eight feet, and this is 

 typical of all. Probably the proper pelagic fauna of other 

 places is due to a constant temperature and food supply that 

 would not exist in these shallow lakes. Yet some of the 

 species of Cyclops which, in other localities have been con- 

 sidered strictly pelagic, seem able to stand the greater changes, 

 and are found here in association with strictly stagnant water 

 varieties. For example, Cyclops leuckarti and Cyclops pul- 

 chellus have been found in marshy places in association with 

 Diaptomus sangui?ietis and Cyclops navus. To such an extent 

 lias this been true that it has been impossible to determine 

 the normal habitat of these species. 



In the ponds and lakes subject to the least change during 

 the year, without regard to size, fewer species are found than 

 in those subject to varying conditions of water supply. The 

 place to look for the greatest variety here is in some pond 

 which does not become quite dry at any season of the year, 

 but comes very near it, and which is marshy in its nature. 



It is very marked that the least variety occurs in the largest 

 lakes. The two largest had but one variety. Two small 

 ponds, supplied by deep wells, and of some depth, had but two 

 species, while most of the temporary or stagnant pools had 

 f >ur or more varieties. The same rule applies also to the 

 Cladoceva. The two largest lakes had one or two species, 

 while the marshy ponds might have six or seven. Of course, 

 the pond must last a considerable portion of the year in order 

 to develop a variety. 



None of the species, so far as I find, can stand a strong cur- 

 rent. Of the millions that must be carried from the slower 

 streams and quieter portions where they abound, none seem 

 to live to reach the larger rivers. I could find none in the 

 Platte, or even in Salt Creek near its month, where it is quite 

 large, and has a strong current. Wherever there are many 

 specimens in a stream, with even a slight current, it is usually 

 found that they have been washed from some quiet pond 

 near at hand. 



The coloring of the specimens taken from the quiet, stag- 

 nant water is much more brilliant than that of those found 



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