4 Maurice Croivthcr Hall 



Some idea of the extent of the infection may be drawn from 

 the fact that on one occasion a single fecal discharge yielded 102 

 gregarines, perhaps a result of the partial sloughing of the intes- 

 tine which Leger and Duboscq (1902) have studied in connec- 

 tion with the gregarines. What the effect on the host of such 

 extensive parasitism with the accompanying rupture of the intes- 

 tinal wall may be is uncertain, and as writers on this subject have 

 pointed out, our knowledge of invertebrate pathology is too lim- 

 ited to judge this point. Rossler (1882), however, in his study 

 of Actinoccphalus Ussidens and Stylorhynchus caudatns, parasitic 

 in the Phalangidae, and Johansen (1894) regarding the new spe- 

 cies, Actinoccphalus goronozvitschi, which he found often packed 

 together in the caeca of Phalangium opilio, both state that these 

 forms occur at times in such numbers as to cause the death of the 

 host. 



Hirmocystis rigida is a fair-sized gregarine, the typical speci- 

 men being about 700 /x long, of which the protomerite is about 

 185 IX and the deutomerite 615 /x. The size is, of course, variable, 

 some specimens exceeding the total length given by 50 or 100 ^a. 

 The breadth of the deutomerite for the typical Specimen is about 

 300 ju, the protomerite being slightly less than this. 



Young specimens are clear, finely granular, and transparent. 

 Later they become opaque and take on a color varying from sul- 

 phur-yellow to orange-red. It is commonly stated, as by Rolles- 

 ton (1888) and Wasielewski (1896), that the color of gregarines 

 is due to the nature of the 'intestinal content of the host, and the 

 fact that practically all the gregarines of one locality were 

 orange-red and those from other localities yellow would seem to 

 indicate that the color follows directly from the food of the host, 

 but the presence of a white gregarine of a different species in the 

 same host with the yellow gregarines would seem to indicate that 

 gregarines of a given species exercise a selective affinity for cer- 

 tain kinds of food material. 



The sporont is notably polymorphic. This is not due to the 

 constant flexion so common in such relatively soft-bodied forms 

 as Grcgarina blattaniiu, but to a more or less permanent variation 

 in shape of the rigid body. The typical form has a subspherica! 



152 



