RECENT FRESHWATER INVESTIGATIONS 331 



winter dormant while frozen in the ice of small ponds which 

 are entirely congealed. 



Wesenberg-Lund (96) emphasizes the adaptations to the 

 climatic conditions of freshwater existence, particularly to the 

 ice, which are necessary in organisms coming from the sea. 

 This necessity is most evident for surface forms and is mani- 

 fested in the formation of winter eggs and winter buds. Land 

 animals must undergo modifications particularly in the organs 

 of respiration to fit them for an aquatic life. 



In reference to the littoral fauna as a whole only a few scat- 

 tered notes are at hand. Various authors have attributed the 

 richness of a lake fauna to the development of the littoral area. 

 Reighard (94a) has expanded the idea to a considerable extent. 

 Others have attributed to the opposite cause the poverty of a 

 lacustrine fauna as "Ward (96d) in the case of Pine Lake. In 

 this connection it has been frequently pointed out that the 

 development of the littoral flora is an exceedingly important 

 factor. On the whole, but little attention has been paid to the 

 littoral fauna as a whole although isolated groups of organisms 

 from it have been carefully studied. When the reverse has 

 been true, the results attained are rather striking. Thus Entz 

 (97) and his colleagues in the investigation of Lake Balaton 

 found an exceedingly rich littoral fauna, and some progress 

 was made in the distinction of shore "formations" and the 

 characteristic fauna of each. Thus France (97) distinguished 

 as protozoan formations, the peat bogs, the muddy shore with 

 reeds, the bottom mud, the sandy and rocky shore, and the 

 plankton. 



The investigation of underground waters has received some 

 attention. In New Zealand, Chilton (94) discovered in sub- 

 terranean streams many forms also common in surface waters, 

 but all pale and transparent. In all the Cru3tacea save one, 

 eyes were entirely lacking, and in that one no retinal pigment 

 was present. On the other hand, the antennae and other ap- 

 pendages were noticeably elongated. In the caverns of the 

 Adelsberg, Schmeil (94) noted that the subterranean Entomos- 

 traca were colorless or pale in contrast with similar forms from 



