176 PROTOZOAL PARASITES 



their anterior ends to form rosettes. Prowazek states that in the 

 rosette condition the living portion of the flagellate resides, as it 

 were, in the long tail-like process. 



Patton divides the life-cycle of H. muscae-domesticae into 

 three stages — the pre-flagellate, flagellate, and post-flagellate. The 

 last two are common, but the first stage is not common, and 

 Prowazek appears to have overlooked it. For convenience I have 

 described the flagellate stage first, and the process of division in 

 this stage is simple longitudinal fusion. The nuclei divide inde- 

 pendently, and the kinetonucleus usually precedes the tropho- 

 nucleus. The latter undergoes a primitive type of mitosis, in which 

 Prowazek recognised eight chromosomes (VII). The flagellum 

 divides longitudinally, and each of the two halves of the kineto- 

 nucleus appropriates one of the halves with its basal granule. 



The pre-flagellate stage, which Patton (1909) describes, usually 

 occurs in the masses which lie within the peritrophic membrane \ 

 They are round or slightly oval bodies (I), their average breadth 

 being 5*5 /x. The protoplasm is granular and contains a tropho- 

 nucleus and kinetonucleus. Division takes place by simple longi- 

 tudinal division or multiple segmentation, and in this manner a 

 large number of individuals are formed (II b and III). These 

 develop into the flagellate stage : a vacuole, the flagellate vacuole 

 (IIl,f.v.) appears between the kinetonucleus and the rounded end 

 of the pre-flagellate form, and in it the flagellum appears as a 

 single coiled thread, which is extended when the vacuole has 

 approached the surface. 



The flagellate form has already been described, and in the 

 concluding portion of the flagellate stage, which, according to 

 Prowazek, is found in starved flies, these forms are found collecting 

 in the rectal region, and attaching themselves by their flagellar 

 ends in rows to gut epithelium. The more external ones begin to 

 shorten, during which process the flagella degenerate (IX) and are 

 shed. Thus a palisade of parasites is formed, the outer ones being 

 rounded and devoid of flagella, and some of them may be found 

 dividing (X). Leger (1902) terms these the "formes gregariennes," 

 and maintains that the existence of these " gi-egarine " forms is a 



1 I assume that Patton refers to this membrane by the term " peritricheal 

 membrane. ' ' 



