No. 2.] FRESH- WATER PROTOZOA. 9 



Following the key I have given brief diagnostic descriptions 

 of the determined genera. In these descriptions I have also 

 followed the plan of Kirchner and Blochmann, in including 

 only the essential characters, leaving out the subordinate de- 

 tails which are liable to confuse the student rather than aid 

 in identification. In the description of the genera only those 

 are described in this preliminary report Avhich have already 

 been actually identified by myself, as occurring in our waters. 

 There are doubtless other genera in Connecticut, which will be 

 found later, and their descriptions will be given in subsequent 

 reports. 



' I have found several types of Protozoa existing in our 

 waters, sometimes in considerable abundance, that do not agree 

 with any described genera. Whether to regard these as new 

 genera or modified forms of described genera I am as yet un- 

 certain. In this preliminary report they are called new genera, 

 and descriptions are then given. No attempt is made at present 

 to give them names, for I regard it preferable to reserve the 

 final descriptions and the naming of such types until a later 

 report, when a longer period of study may enable me to de- 

 termine more accurately whether these genera are connected 

 by intermediate grades with any of the types already described, 

 or whether they should be regarded as really new. 



Descriptions of species are wholly omitted in this report 

 The Protozoa are known to be widely variable, and it is, there- 

 fore, always a matter of great difficulty to determine where 

 to draw the limits between species. Two different attitudes 

 toward this question may be adopted. One is to describe each 

 distinguishable type as a separate species, and the other to 

 group large numbers of closely allied forms together under 

 the name of one species, even though they show wide varia- 

 tions. The latter method appears to me, on the whole, pref- 

 erable ; but if it is to be done, it can only be done after a long 

 study of the different varieties that may be found, a study much 

 more extended than it has been possible as yet to give to the 

 subject. Moreover, the specific descriptions of Protozoa are 

 so widely scattered in literature that it is a great task to obtain 

 them all. Up to the present time I have not been able to 

 search all this literature, in order to identify all the species 



