COLLECTION OF BDELLOID AND OTHER ROTIFERA. 207 



the commoner and cosmopolitan forms and of a great many of 

 the rarer species. 



If, however, Eousselet's lists are examined from the stand- 

 point of the habitat in which the various new species have been 

 met with, it will be apparent that while undoubtedly much the 

 greater proportion of these recent discoveries have resulted from 

 collections in areas not previously searched, nevertheless quite 

 a large number of the species have been found in habitats which 

 are more or less outside the ordinary activities of the pond-life 

 worker. 



These notes on the collection of Rotifera will accordingly deal, 

 not only with the customary methods of Pond work, but also 

 with some less usual methods and with work which has little 

 or nothing to do with ponds at all. The Rotifera which are 

 to be obtained by the latter methods belong principally, but 

 not exclusively, to the order of the Bdelloida, to which I have 

 given my greater attention for many years past. 



In speaking of Pond work, I use the phrase in its most com- 

 prehensive sense. I include in it not only the collection from 

 pools and ditches of all sorts, sizes and positions, but also from 

 running waters, and especially the smaller streams, rivulets or 

 mere runnels, from lakes, reservoirs and canals ; and even 

 from rock-pools and brackish waters. 



The methods of collection which I refer to as customary are 

 the use of the net, the use of the dipping bottle, and the selec- 

 tion of portions of water-plants. These several methods are to 

 some extent provided for in the ordinary pond collecting outfit, 

 and it seems needless to describe them in detail ; but some 

 suggestions with regard to the net and its use may be worth 

 consideration. 



The most suitable form of net for the capture of Rotifera 

 depends largely upon the character of the body of water in 

 which it is to be employed, and upon the habits of the species 

 which it is expected or hoped to capture. The habits of the 

 Rotifera in their turn depend principally upon the nature and 

 abundance of their special food. Those species whose food 

 consists of smaller or weaker organisms, either swimming or 

 floating, mostly swim themselves in search of their prey, and 



