A H.EMOaREGARINE OF MAMMALS 109 



hours or more, either at room temperature or in the incubator at 37° C, no change 

 results. 



If, however, sonic tinit^ elapses, say twenty-four hours, hcforc the mite lie I'xainineil, 

 numerous vermicnle forms are sometimes found in fairly active motion, together with many 

 unchanged trophozoites. These vermicules bend themselves from side to side and also 

 progress amongst the altered or disintegrated blood corpuscles. They do not exhibit 

 the "euglenoid" movements shown so markedly by the free vermicules found iu the jerboa, 

 but mertdy glide about. On staining it was noticeable that their cytoplasm was quite 

 free from chromatin granules, though it stained a pale blue as in the "jerboa" vermicules. 

 This agrees with the characters of the vermicules from the louse described by Christophers. 

 On the other hand, from measurements I have made, I hud these "mite" vermicules just 

 about the same size as the '•jerboa" vermicules, whereas Christophers found the "louse" 

 vermicules distinctly larger than those present in the gerbil. I have now examined a 

 considerable number of mites both gorged and ungorged, and at various times after feeding, 

 and have carried out a few experiments similar to those conducted by (Christophers with 

 lice, but [ have not so far been able to absolutely satisfy myself that cyst formation occurs. 

 One is apt to be deceived, as large cysts, looking to the naked eye like minute white 

 spheres, are sometimes obtained from the mites, and on examination these cysts are seen 

 to be packed with spherical bodies. The latter, however, appear undoubtedlv to be some 

 form of fat cell. They are highly refractile, somewhat resemble large oil globules, and their Possible stage 

 contents dissolve on the addition of ether. Once, and once only, in a case where no large 

 cyst was seen, I found small bodies like cysts and apparently containing crescent-shaped 

 forms, the whole appearance being rather like Fig. 16 in Christophers' monograph, 

 which illustrates zygotes containing sporozoites. There was, however, nothing so definite 

 as the well-marked cysts found in the flea, and I am not inclined to lay any stress on this 

 observation. I kept the slide of citrated blood from the mite for sixteen hours in the 

 hot incubator at 37° C, and thereafter could not find any of these cysts (?) in the 

 preparation. Captain Cummins, to whom 1 showed them, agreed that they resembled 

 Christophers' illustration. 



A fact of interest is that, in one case on examining comparatively fresh citrated 

 blood expressed from a mite which had fed five hours before on a jerboa with a moderate 

 infection, I noticed several large vermicules dragging small clumps of red cells after them, 

 there being a distinct interval, possibly bridged by an invisible gelatinous thread, between 

 the narrow extremity of the vermicules and the corpuscles. Continuing to watch one of 

 these vermicules I saw it start curious rotatory movements exactly like those Christophers 

 describes in the case of the vermicules derived (?) from the sausage-shaped bodies in the 

 small cysts found in the louse. I watched it for quite a long time. As a rule it was 

 the parasite itself which rotated, using the red cells as a fixed point on which to turn. 

 After a time motion ceased and the vermicule changed in shape, becoming swollen at one 

 end. Many ordinary free trophozoites were also present in this blood in which no vermicules 

 could be seen after it had been kept all night at 37° C. These results, though by no means 

 conclusive, are somewhat suggestive, and I believe the mite may yet be found also to serve 

 the part of an intermediate host. Latterly I have been unfortunate in not being able 

 to secure jerboas with large infections of the h£eniogregarine. Given a good ease, it is 

 possible that one might find the same cystic stage as Christophers has described for 



