No. 465.] ZVTERRELATIONSHIPS OF SPOROZOA. 623 
spores are assumed to reach the exterior with the evacuations of 
the host. For the tissue-infesting species, however, there are 
no natural channels. Where the parts attached are superficial, 
it is conceivable that the tumors which so frequently occur in 
Myxosporidian infection may break to the exterior. In this way 
the spores would be set free. But in deep-seated infections the 
conclusion seems inevitable that the death of the host is neces- 
sary. This conclusion is supported by the fact that extensive 
infections are generally fatal. 
The Myxosporidia attack cold-blooded vertebrates and arthro- 
pods. The Sarcosporidia confine their attentions to birds and 
mammals. They are very abundant in the visceral muscles of 
sheep and swine. While their spores differ from those of the 
Myxosporidia, the animals themselves are morphologically a 
good deal like those members of the last-named group which live 
in cysts or in the state of diffuse infiltration. Additional data 
regarding them are a crying need and at present all that can be 
said is that they have probably evolved from Myxosporidian-like 
ancestors. The Haplosporidia may be dismissed at once. Our 
knowledge is too scanty to warrant any generalizations. 
It is possible, however, to compare the Neosporidia with the 
Telosporidia. Taking the free-living Myxosporidia on the one 
hand, and the Polycystidea on the other, we fail to detect any 
points of similarity. The habitats, life histories, and reproduc- 
tive processes are wholly different. There is no morphological 
likeness in any of the stages, from spore to trophozoite. Ina 
few cases, gregarines are almost amoeboid and can protrude 
pseudopodia. The Monocystids, also, are coelomic parasites and 
some species live in the organic cavities of their hosts. But this 
appears to be the sum total of the evidence indicative of any 
connection between the two groups. It is palpably insufficient. 
Unless, then, future discoveries of a fundamental nature shall 
be made, there seems ample warrant for the view expressed by 
Mesnil and Doflein. This is that the Telosporidia and Neospor- 
idia are not genetically connected. Accordingly, at least for the 
present, we should use the term Sporozoa merely as a convenient 
cloak. It serves to cover certain Protozoa which cannot be 
placed in any of the other Protozoan classes. It is not so long 
