82 THE LIFE OF DEVILS LAKE 



Figure 22. Seasonal distribution of rotifers in East Lake. 



be significant is shown in plates 18 to 21 and will be discussed 

 briefly in the annotated list. 



Absent, or practically so, in winter, the rotifers develop rapidly 

 in early summer and may reach their maximum for the entire year 

 by the first of June. There are usually two maxima, one in June 

 or July and another in August, but in 1913 there are three sueh 

 periods, the last one appearing about October 6, which is unusual. 

 The curves show very sharp breaks, indicating rapid development 

 and equally rapid disappearance. 



While the rotifers of Devils Lake are mostly fresh M^ater types, 

 like rotifers in general elsewhere, there are a few which are marine 

 as well as fresh water. These are Colurella adriatica, colura, Brach- 

 ionus plicatilis, Notholca striata thalassica and Pedalia fennica. 

 Collotheca cornuta, Brachionus calyciflorus pala, Polyarthra trigla, 

 Keratella cochlearis, and possibly Asplanchna silvestrii* occur in 

 both fresh and brackish water, while Brachionus satanicus and B. 

 pterodinoides, both of them new species, belong in the latter class, 

 judging from their distribution in the complex and its adjoining 

 waters. 



The widespread distribution of so many species in both the 

 brackish and fresh water lakes of the complex indicates the 

 adaptability of the group to widely varying environments; the 

 apparent restriction of some to one or a few lakes, being due 

 possibly to the incompleteness of the investigation. The rotifers 

 show marked light reactions, a discussion of which has already 

 been given.** 



Rotifers occur occasionally in oxygen free water.*** 



The annotated list follows: 



Cephalodella catellina. Occurs occasionally in the main lake, 

 where it is of widespread distribution. Reported also from East 

 Lake. 



Diaschiza sterea. Widely distributed in main lake. Reported 

 also from East and Mission Lakes. 



♦The character of the Chilean lake from which this species was first taljen Is 

 not known. 



**See p, 46. 

 •♦♦See p. 107. 



