192 ILLINOIS BIOLOGICAL MONOGRAPHS [402 



low and scarcely noticeable in the satellite. The deutomerite is stout, 

 three fourths as wide as long; it increases gradually in width up to the 

 beginning of the posterior third of the body, when it becomes rapidly nar- 

 rower, ending in a very broadly rounded extremity. The protomerite of 

 the satellite is larger than that of the primite, which possibly indicates 

 sexual dimorphism. The primite and satellite are not well interlocked. 



The endocyte of the primite is dense and is not visible in vivo. The 

 endocyte of the satellite is paler, revealing the presence of a spherical nu- 

 cleus. Trophozoite and cysts were not found. 



A table of measurements of one association follows in which all di- 

 mensions are given in microns : 



Primite Satellite 



Length protomerite _. 30 45 



Length deutomerite — 230 165 



Width protomerite 75 110 



Width deutomerite 180 155 



Total length sporont „ 260 210 



JRatio 



length protom. : total length „ 1 :8.6 1 :1.4 



width protom. : width deutomerite 1 :2.4 1 :1.4 



, GREGARINA PLATYNI nov. spec. 



[Figures 262, 263, 264] ^. 



Host: Platynus ruficoUis Marsh (Det. Dr. E. P. Felt). ^ 



Location: Oyster Bay, L. I., October, 1915. 



The host of this species is a very small black beetle which flew in 

 my study window one evening. Several hundred parasites were found in 

 the intestine of the single host. 



The sporonts are biassociative. They are elongate cylindrical in 

 shape and generally lie in a slightly curved position. The largest associa- 

 tion measured 610/x in length while sporonts averaged SOOyu, in length and 

 60/x in width. The average ratio of length protomerite : total length 

 sporont : : 1 : 4.3 and the ratio width protomerite : width deutomerite 

 : : 1 : 1. The protomerite is characterized by a constriction in the mid- 

 dle which is deep and conspicuous in sporonts of all ages and the proto- 

 plasm is much less abundant above the constriction than below. There is 

 a deep constriction at the septum between protomerite and deutomerite. 

 The apex of the protomerite is rounded, sometimes rather acutely while 

 the deutomerite is cylindrical, attaining a maximum width just behind 

 the constriction and tapering slightly in the posterior two thirds. The 



