1903.] NATURAL SCIENCES OF PHILADELPHIA. 41 



LIST OF THE POLYCYSTID GREGARINES OF THE UNITED STATES. 



BY HOWARD CRAWLEY. 



I. 



The polycystid gregarines of the United States have as yet been but 

 very Httle studied, and the Hst here given, which I beheve to be com- 

 plete, contains but twenty-eight species. Of these, six are also found 

 in Europe and were first described from there. It is to Prof. Leidy that 

 we owe the better part of our knowledge of the American forms. Ten 

 species were described by him in accounts pubhshed in the Proceedings 

 of the Academy and in the Transactions of the American Philosophical 

 Society from 1848-1889. In addition to these, four more species are 

 described and figured by Leidy in manuscript notes now in posses- 

 sion of the Academy, access to which I owe to the kindness of the 

 Secretary, Dr. Nolan. Of the remaining eight forms, one was de- 

 scribed by Porter, and seven were found by me in animals collected 

 at Wyncote, Pa., and Raleigh, N. C, during the past year. 



The four forms described in Leidy's manuscript, and the one by Por- 

 ter, were not named. I have accordingly created new species for them 

 which, with the seven that I discovered, makes twelve new species. 

 Although the method of naming a gregarine after its host has been ob- 

 jected to by Schneider, it appears to me the most advisable, and it has 

 accordingly been followed. Considerable difficulty was experienced, 

 however, in determining to wliich genera these new species belong. 

 The generic characters of gregarines are mostly those of the cysts and 

 spores, and I was particularly unfortunate in failing to obtain these 

 stages. In several cases it has been possible to judge, even mthout 

 these criteria, what the correct genus is, and such forms have been 

 placed where they probably belong without question. Where, how- 

 ever, there was considerable doubt, a question mark has been placed 

 before the generic name. 



II. 



The following is a list of the Arthropoda found to contain gregarines, 

 the first column giving the number of individuals examined, the second 

 the number parasitized : 



