No. 465]. ZVTERRELATIONSHIPS OF SPOROZOA. 621 
these hypotheses are open to objection in that they are based 
almost exclusively on the reproductive phenomena. They both 
involve the evolution of a more from a less complexly organized 
parasite. I have endeavored to show that this is contrary to 
what experience teaches us to expect. In our classification of 
the Metazoa morphology is given first place and it should not be 
. neglected in a consideration of the Protozoa. The remarkable 
character of the reproductive phenomena displayed by the 
Sporozoa has, I think, given them an undue importance. The 
form of the adult animals has, in any attempt at a classification, 
at least equal value. s 
We have now to consider the Neosporidia. This subclass is 
but poorly known. As shown above, it consists of three orders, 
the Myxosporidia, the Sarcosporidia, and the Haplosporidia. 
The Myxosporidia are characterized by their peculiar spores, 
which bear a close resemblance to the stinging cells of ccelen- 
terates. The spore consists of a bivalved shell, inclosing the 
sporoplasm and the polar capsules. The polar capsules, of 
which there may be from one to four, are tightly coiled filaments 
which occupy vacuities in the spore substance. Acted upon by 
the digestive juices of the host, the spore shell opens and the 
filaments are everted. By means of these filaments the spore 
is held attached to the intestinal epithelium of the host, and 
the sporoplasm escapes as a minute amabula. Freed on the 
surface of a host cell, it works its way within and comes to rest. 
The nucleus presently divides, then the cytoplasm, and each 
spore thus produces a number of bodies which are at least the 
analogues of the Coccidian merozoites. They scatter through- 
out the host and each gives origin to a trophozoite. The tropho- 
zoite grows larger, becomes multinucleate and soon begins to 
form spores. These, eventually reaching the exterior, are fitted 
to infect new hosts. 
The above outline of the life history is that given by Doflein. 
It is to be observed that there is no sexual process. Doflein, 
however, considers it possible that either the spores themselves 
may conjugate very shortly after their escape from the spore 
shell, or else that this process may take place between the young 
trophozoites. This he advances merely as a surmise, there 
being no observational evidence. 
