18, 4 Haughwout: Human Coccidiosis 465 
The structure of the fully developed cyst shows considerable 
variation as regards the shape and size of the odcysts, the 
character and amount of sporocystic residuum present, and 
the arrangement of the sporozoites. I gather from reading 
Noc’s paper, that he is under the impression that the odcysts 
increase in size as they reach full development. At the present 
time I am inclined to doubt if this is really so, but the whole 
matter of the dimensions of these cysts is a subject I am pur- 
posely not taking up in this paper, and I shall defer further 
consideration of it until I have had the opportunity to go over 
the measurements I have already made and the measurements 
of some preserved material. It has occurred to me that there 
may be races within these species, characterized by the size of 
their cysts. The difficulty lies in making accurate calculations 
of the size of cysts that assume such irregular outlines. 
It will be seen, by viewing the figures of some of the fully 
developed cysts (Plate 2, figs. 5 to 11, Plate 3, fig. 10), that 
the sporocystic residuum shows considerable variation in char- 
acter and amount. In some cysts (Plate 2, figs. 6, 7, 8, and 10) 
it is fairly rich and normal-appearing, while in others (Plate 2, 
figs. 5, 9, and 11) it is formed largely of fine, dark granules and 
is scant in amount. In others (Plate 3, fig. 10; Plate 2, fig. 12), 
it appears in the form of dull, hyaline-looking bodies. Both 
these cysts had been subjected to dessication for one week. 
These are appearances that are not restricted to this species, 
but may be seen in other species of coccidia. 
DEVELOPMENT OF THE CYSTS AT 10° C 
A study of the development of the cysts at a constant tem- 
perature of 10° C. was rather interesting. One of the stools 
studied thus was that of March 21, a portion of which was 
placed in the ice box a few minutes after it was passed. Twenty- 
four hours later a sample was taken from the ice box, but none 
of the cysts had passed beyond the early zygote stage. On 
the morning of March 23, numerous, well-advanced sporoblasts 
were seen, also some zygotes, apparently in good condition. 
There were very few degenerating cysts. Odcysts containing 
sporocysts were found on the morning of March 24. The 
sample taken from the ice box on that day was laid aside on 
the laboratory table overnight (temperature, BO” 40 .32°.C.). 
When it was examined the next morning (temperature, 
