612 THE AMERICAN NATURALIST. (VoL. XXXIX. 
Of all the Telosporidia, the Polycystidea stand highest in 
organization. Their name indicates the fact that they are 
divided into parts. The division is longitudinal and the parts, 
from before backward, are termed epimerite, protomerite, and 
deutomerite. The epimerite is an organ of attachment, com- 
parable to the suckers of Trematodes and the hooks of Cesto- 
des. It is peculiar to the Polycystidea and has evidently been - 
evolved to meet the requirements of an intestinal life. The 
protomerite and deutomerite are the two “cysts” of the 
gregarine body. The latter is nearly always much the larger, 
and contains the nucleus. 
From without inward, the ectosarc of a Polycystid gregarine 
shows epicyte, sarcocyte, and myocyte. The epicyte is a mem- 
brane of some formed substance. Its function is probably to 
guard against the too rapid action of the fluids of the host's 
intestine. The sarcocyte in protoplasmic and an ingrowth 
from it forms the septum. which separates the protomerite from 
the deutomerite. The myocyte is a muscular system of longi- 
tudinal and transverse fibers. By means of various contractions 
of these fibers gregarines are able to change shape and to dis- 
play locomotor movements. 
It is thus seen that as regards both form and anatomy the 
Polycystids are somewhat complicated animals. They are also 
exclusively intestinal parasites and there is neither change of 
hosts nor alternation of generations. If then our criteria be of 
any value, the Polycystid gregarines are the least modified of the 
Telosporidia and stand nearest to the stem from which the 
entire subclass originated. Assuming this as a working hypoth- 
esis, it remains to be seen if the remainder of the Telosporidia 
can be derived from them. 
Grégarines develop from a minute protoplasmic body, known 
as a sporozoite. The sporozoite is piriform or vermiform. At 
the anterior end, the protoplasm is stiffened and forms the so 
called rostrum, by means of which the organism is able to work 
its way into an epithelial cell of the host's intestine. Asa rule, 
penetration is only partial and the Polycystidea, with the excep- 
tion of a single family (the Stenophoridz), are never cell para- 
sites. In its chosen place, the sporozoite grows to be an adult 
