34 
the stomach wall in the body tissues of the mite. ' They are granular 
and deeply colored by basic stains. 
The exact manner in which the basement membrane is penetrated 
by the parasite is unknown. Probably the contraction of the delicate 
muscular envelope of the alimentary sac causes the parasite to be 
forced through the spot, weakened by its encroachment upon the base- 
ment membrane. At any rate the ookinets are found free in the 
body cavity. As shown in the description of the anatomy of the mite 
the body cavities represent the numerous small spaces between the 
various organs, and between these and the chitinous body envelope. 
In an}^ of these spaces, in the investing membrane of the salivary 
glands, or within the sheaths of the muscles inclosed in the body of 
the mite, the ookinets may be found. 
After thus wandering about in the body tissues the ookinets become 
stationary and undergo a remarkable change. Coincident with an 
increase in size of the plasma, in which large round granules begin to 
appear, the karyosome becomes greatly enlarged, exceeding in size the 
original nucleus. The nuclear membrane is but slightly larger than 
this giant karyosome, which may measure 10 micra in diameter. 
\Yhen the parasite has reached a diameter (in the fresh specimen) of 
about 60 to 75 micra, it becomes oval or spherical and a delicate cyst 
wall makes its appearance. This stage is observed in mites four and 
five days after infection. It is evident that the large karyosome is 
the forerunner of active multiplication of the nucleus of the encysted 
parasite, which is now termed a sporont (Liihe) and the cyst an oocyst. 
In sections of mites showing more advanced stages, the parasite 
often appears oval or flattened by reason of the restraining action 
of the various organs or tissues upon its growth. In fresh dissections 
of mites the sporonts are conspicuous by reason of their size, spherical 
form, and granular structure (pi. xiv). The cyst wall is often A^ery 
much larger than the parasite it contains, the latter appearing to float 
freely within it. The sporonts at this stage measure from 100 to 150 
micra in diameter. Upon reaching approximate!}^ tliis size the 
nucleus undergoes dhdsion into two. The dhdsion is repeated and 
the daughter nuclei migrate to a position near the surface of the pro- 
toplasm, wliich forms a perfect sphere (pi. xiv, figs. 1-2). Nuclear 
division continues until a large number of nuclei are formed, all 
located in a superficial layer of the protoplasmic mass. The oocyst 
reaches a maximum diameter of 200 to 250 micra, although usually 
somewhat smaller. 
In mites infected six or se^mn days previously the surface of the 
sporont is covered Avith budlike projections (pi. xia% figs. 3-4), each 
of which contains a nucleus. A little later the buds become more 
prominent and elongated and break off from the central mass. A 
large number (50 to 100 or more) of oval bodies are thus formed, each 
