DISTRIBUTION OF SPECIES. 63 



In the discussion of the annual occurrence of the various or- 

 ganisms, these differences have already been noticed in detail, 

 but it may be well to present them in a summarized form. 



In the case of plants the distinction between the different 

 classes of lakes is more quantitative than qualitative, for the lit- 

 toral conditions of deep lakes are such as to permit a great 

 variety of forms, although they do not allow any large multipli- 

 cation of numbers. So that while the plant production in the 

 shallow lakes is vastly more prominent than in the deep lakes, 

 most of the species of the shallow lakes can be found in greater 

 or less numbers in the deep lakes. 



Clathrocystis and allied forms, and Oscillarw, however, may 

 be considered peculiar to shallow lakes. Gloiotrichia, too, is a 

 shallow lake form, but not exclusively so, as it occasionally 

 occurs in large numbers in a deep lake. 



Anabaena is the ordinary form of the "bloom" of the deep 

 lakes but it is not peculiar to them, but is even more abundant 

 in the shallow lakes. Of the protozoa, Ceratium is character- 

 istic of the deep lakes. It occurs in shallow lakes, but in lim- 

 ited numbers. I do not find that Dinobryon can be considered 

 as characteristic of any class of lakes, although European, au- 

 thors have made the distinction between Chroococcaceae and 

 Dinobryon lakes. So far as our Wisconsin lakes are concerned, 

 Dinobryon can not be said to be characteristic of any class of 

 lakes. Of the rotifers, Notholca longispina, while found in 

 both classes of lakes, is found characteristically in the deep 

 lakes; there it is common and sometimes in great numbers. 

 Conochilus, while not found in all shallow lakes, seems, never- 

 theless, to be pretty well confined to this type. Of the other 

 rotifers, it can hardly be said that they are characteristic! of 

 either class of lakes. 



Of the Diaptomi, D. sicilis belongs distinctly to the large 

 deep lakes although it may be found as a migrant in some of the 

 Michigan lakes, connected with the Great Lakes. D. minutus 

 belongs to the large deep lakes but not exclusively so, for in 

 northern Wisconsin and northern Michigan it may be found in 



