251] STUDIES ON GREGARINES— WATSON 41 



not the same although the same species or genus of host is involved; 

 such unlike parasites have been separated. For example, Phialoides 

 ornata Leger and Gregarina brevirostra Kolliker were regarded as 

 synonymous because they infect the same host. In some instances Labbe 

 regarded as synonymous species which actually belong together; for ex- 

 ample, Actinocephalus lucanus Stein and Stephanophora radiosa Leger, 

 which are identical, the species now being known as Actinocephalus coni- 

 cus (Dufour) Stein. 



The law of priority has been adhered to strictly and many parasites 

 known by later assigned names have been referred to names given to 

 them many years before, e. g. Actinocephalus conicus which was long 

 known as Actinocephalus lucanus. Labbe in most instances calls such 

 species by the later assigned names in his treatise. 



In the descriptions of species, well developed sporonts have been 

 taken as the standard except where such have not been described, these 

 rare instances being noted in the synopsis. Shape of the cephalonts is 

 often quite unlike that of the sporonts and thus of no systematic value 

 in diagnosis. Whenever the epimerite is not mentioned in the literature, 

 as is often the case, the generic determination of the author is based on 

 other characters. The sporonts are often polymorphic and the synopsis 

 records are based on expanded, quiescent, and, as far as known, normal 

 specimens except where the polymorphism is marked. In these instances 

 such facts are noted. 



In the description of each new species, I have given measurements 

 of only a few large, typical sporonts. These are taken from records of 

 the measurements in most instances of twenty-five or more animals. In 

 most published descriptions the length and width of one sporont only is 

 stated, generally of the largest one observed and the ratios of various 

 parts are based on this one parasite. 



As the discovery of new species proceeds, I am of the opinion that 

 many will be very similar to others already described and not easily dif- 

 ferentiated from them unless a wide range of measurements and ratios 

 is taken from parasites in different hosts and selections made therefrom 

 for use as a table. This applies in particular to the genus Gregarina, 

 where differences between species appear to be limited. One observer 

 might find the maximum length to be a and the ratio of the two parts as 

 1 :2. Another worker on the same species might find his largest specimen 

 to be 2a long and the ratio of parts as 1 :3 and describe the species as dif- 

 ferent from the former. A table showing lengths and ratios selected 

 from measurements of many parasites in the same host and from as many 

 hosts and under as varying conditions as possible (habitat, season, etc.) 

 eliminates the danger of duplication of species. 



I have differentiated new species in the same genus by the following 



