STRUCTURE, ETC., OF PLEISTOPHORA PERIPLANETM. 617 
spores themselves. The parasite lives freely in the lumen of 
the alimentary canal and the Malpighian tubules. Examina- 
tion of the fresh tubule usually shows the trophozoites crowding 
up against the sides of the passage, although they are fre- 
quently present in sufficient numbers to block the whole 
lumen completely. When the trophozoites are present in 
any number the cells of the tubule are comparatively clear 
and hyaline, the very numerous grauules ordinarily present 
in the cells of uninfected tubules being conspicuous by their 
absence. 
Examination of the fresh tubules and sections, both trans- 
verse and longitudinal to them, has failed to reveal the 
presence of intracellular stages. he parasite appears to be 
wholly extracellular, and, in this feature, differs from the rest 
of the Cryptocystes, which are by definition cell parasites. 
The parasite is not apparently fatal to its host. Every adult 
Periplaneta examined contained the parasite, and frequently 
great numbers of it, without any apparent inconvenience. 
* The reason of this is probably to be sought in the fact that 
although the parasite may be present in very large numbers 
its presence is confined to comparatively few of the Malpighian 
tubules, nor do the tubules themselves, however strongly 
infected, appear to be destroyed. 
Confusion with tissue elements or with any other members 
of the singularly rich and varied fauna harboured by the 
cockroach is impossible on account of the very characteristic 
appearance of the trophozoites, more particularly when they 
are stained with Giemsa’s eosin-azur solution. As before 
mentioned, every adult cockroach examined contained the 
parasite in larger or smaller numbers. The very youngest 
individuals still possessing the hght brown tint characteristic 
of the infant cockroach were alone found to be uninfected. 
Spores occur regularly in the feces, 
For examination of the living plasmodia the Malpighian 
tubules were freed from adhering fat-body, cut in small pieces 
and examined in normal salt solution. Much of the structure 
revealed in the stained preparation can be made out in the 
