is, 4 Haughwout: Human Coccidiosis 459 
says the cysts measure from 25 /*, to 33 y. in length and that they 
have a breadth at the widest part of ca. 12.5 //, to 16 (i. That is 
to say, the width of the cysts is approximately half their length. 
However, as, he has pointed out and as my illustrations show, 
the relative dimensions are not constant, although the long and 
slender forms predominate over those that are short and plump. 
In freshly passed stools the zygotes are practically unde- 
veloped, and may show very little shrinkage away from the walls 
of the oocyst. However, one not infrequently picks up cysts that 
have undergone sporoblast formation, but that is the limit of 
development in the freshly passed stool. The cell body is 
coarsely granular, has a distinct greenish tint and, under suit- 
able illumination, the mass shines like a gem. The resemblance 
to certain plant forms found in the faeces is rather striking at 
first, but one soon becomes able to pick them out from the gen- 
eral collection of plant and animal forms. 
SPOROBLAST FORMATION 
The preliminary stages of spore formation appear to take place 
rather early, and may be seen in some cysts within two hours 
after the stool is passed. Meanwhile the protoplasmic mass 
changes considerably in shape and shrinks away from the cyst 
wall rather rapidly, finally forming a practically spherical mass 
in the center of the cyst. A clear area often appears in this 
mass, toward the center, as if the granular inclusions had been 
forced away from the center (Plate 1, fig. 1). This, may or 
may not mark the site of the nucleus. Frequently, however, 
two or more of these clear areas form in the cell (Plate 1, figs. 2 
and 3) , and I am inclined to suspect that the appearance may be 
connected with cylosis, which becomes fairly active in the cell 
at this stage of development. The spherical form assumed, the 
cell appears to lose much of its passive nature. It undergoes 
almost constant change of form. These changes are slow, very 
much in the nature of the movements of leucocytes, or some 
of the very sluggish amcebse, but they can be followed, neverthe- 
less. The protoplasm is in a condition of constant though 
slow cyclosis in which the granules are circulated round about 
through the cell. On the outer aspect, from time to time, appear 
clear, hyaline processes, devoid of inclusions, that superficially 
resemble pseudopodia (Plate 1, fig. 4). These may also appear 
in the early sporoblast stages as is suggested by Wenyon’s 
figure (fig. 2, p. 625). (16) These form slowly and appear to 
develop more by the retraction of the endoplasmic granules from 
