14 ERNEST WAEREN. 



irreater number of these nuclei must be absorbed or fuse 

 together, on the transformation of the sporozoite into the 

 trophozoite. 



It is highly remarkable that the formation of a cyst-wall 

 is such a variable character. The cyst may be quite thin, or 

 it may attain a thickness of 6 ^ or more. Encysted and non- 

 encysted specimens frequently occur in the same host. The 

 character of the trophozoite and the spores ultimately pro- 

 duced appear to be quite the same in either case. 



I have noticed that in the same host those specimens which 

 are encysted tend to form their spores more slowly than those 

 which are non-encysted. For example, in one case there 

 were some twenty non-encysted bodies which had completely 

 divided up into spores, while the remaining eight bodies, 

 which were surrounded by a thick cyst-wall, had not become 

 split up by the trabeculas. 



I have not had sufficient material to test the matter in a 

 practical manner, but I suggest that the thick cysts are 

 formed so that if the pool should dry up in Avhich the host is 

 living the trophozoite enclosed would be able to resist a 

 considerable amount of desiccation. On falling into water 

 the encysted trophozoite would, without doubt, quickly break 

 up into spores which would be liberated by the bursting of 

 the cyst. 



The spores themselves are only enclosed by a very thin 

 spore-membrane, and it is extremely improbable that isolated 

 spores could resist desiccation. 



The cyst-wall is apparently homogeneous and is tough and 

 elastic. It tends to break up under the knife of the microtome. 



(4) Affinities of the organism. — The present observn- 

 tions throw considerable light on tlie nifinities of the organism. 

 The genus has been placed under the provisional order of 

 Haplosporidia, which includes a number of allied forms. 



Bert rami a kirkmani exhibits undoubted affinities with 

 the Sarcosporidia, but it differs from them in that the 

 trabeculae divide the trophoplasm into single spores, and 

 not into pansporoblasts. No trace of a polar capsule, or even 



