35 
of which contain a nucleus. These bodies represent sporoblasts and 
measure about 10 by 15 micra. 
When obtained in the fresh condition, by gently teasing apart - 
mites in 0.3 per cent salt solution the sporonts are perfectly spherical 
or ovoidal (pi. xiv), with a delicate cyst larger than the sporont. In 
the large budding forms (pi. xiv) the central granular part becomes 
softened and gradually liquefied, the stored-up material being utilized 
in the growth of the sporoblasts. Very slight pressure is sufficient to 
rupture the sporont, causing the escape of the fluid contents and the 
collapse of the superficial portion with the attached sporoblasts. In 
sections this collapsed condition always exists, and the flattened 
sporonts on cross section show usually two rows of sporoblasts with 
the attached ends adjoining, suggesting a fern leaf in appearance 
(pi. XYii, fig. 5; and pi. xi). 
The subsequent development of the sporoblasts is traced in various 
stages in pi. xviii. The nucleus divides and subdivides, the daughter 
nuclei arranging themselves at the poles. A little later a cyst wall is 
formed around each sporoblast. 
The nuclei become the nuclei of the sporozoites, the protoplasm of 
which is split off from the central mass as short rods (pis. xvi and 
xviii), which increase in length and graduall^^ envelop the dimin- 
ishing central ‘‘ rest-body,^ ^ like fingers. With increasing growth of 
the sporozoites at the expense of the “Vest -body,’’ the latter is 
eventually reduced to a small, round, granular mass. The sporozo- 
ites fill the interior of the cyst, which measures on the average 25 by 
30 micra. They are arranged in two general groups, occupffing the 
two halves of the cyst, as shown in pi. xvi, fig. 12-14, the adjoin- 
ing extremities of sporozoites interlocking. This arrangement does 
not always persist, however, since later they may be mixed up 
mdiscriminately and retain mereW a general direction corresponding 
to the long axis of the cyst. Wlien the cysts are ruptured in salt solu- 
tion, the individual sporozoites appear as cresent or club-shaped 
bodies (pi. xvi, fig. 1-2). The nucleus, spherical in form, is located 
nearer the smaller extremity. The thicker and more rounded end, as 
will be seen later, is the anterior. The protoplasm is highly refractile. 
The measurements are 14 micra in average length, by 5 micra in 
greatest breadth, tapering to 2 micra at the narrow posterior 
extremity. 
The rest body persists as a round granular body about 6 micra in 
diameter. The fully developed cysts are found in mites from ten to 
twelve days after feeding. The number of sporozoites is from 12 to 
20 in each cyst ; 16 is the average; occasionally as many as 24 are en- 
countered. The cysts which contam the larger number are elongated 
and often distinct^ bent in the middle. In addition to these, small 
spherical cysts containing about 10 sporozoites are sometimes met 
