THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 99 
infection of epithelium. The typical myxosporidian spore-form is 
accordingly not of such preéminent importance. Further: 
Whether the differentiation of the Sporidia, heretofore principally based upon the 
structure of the spore, will permit itself to be maintained is a matter for zoologists. 
The following investigations show too often how little stress is to be laid upon this 
mark alone, and what variations occur through adaptation. 
Compared with the Gregarines, the Myxosporidia show their lower 
position by the lack of constant body form. 
In the second edition of the same work (1891, pp. 7, 8, 10) he reduces 
his family Sporidia to the rank of a subfamily of the family Coccidia. 
He regards the “psorosperm” as a resting spore, and Says it may be 
the equivalent of the individual falciform germs of the Sarcosporidia. 
The capsules, he says, also occur in the sarcosporidian spore (see p. 88), 
The following is, I think, a fair summary of the evidence: 
The Myxosporidia differ from the remaining Sporozoa in the multi. 
nucleate amcebiform adult, the pansporoblastie spore formation, and 
especially in the capsulate spores, which never contain falciform germs. 
At the same time the consensus, and I believe the evidence, favors 
their retention in the Sporozoa, of which they form a rather aberrant 
subclass. 
As regards the relation of the Myxosporidia to the Myxomycetes, is 
there any evidence that the myxosporidium is a plasmode? In the 
diagnosis of the myxomycete plasmode the following are the most 
important points: 
(a) Actual observation of plasmode formation by fusion of individuals. 
Now, not only has this never been seen! in the Myxosporidia, but the 
multiple nuclei of the myxosporidium are known in several cases to 
(and in all probability always do) originate by the division of the primi- 
tive single one. 
(6) The presence of various shades of red, brown, or black pigment. 
This has never been seen in the Myxosporidia. All pigment there found 
appears to be of extraneous origin.? 
Add to this the differences in the methods of spore formation (and 
particularly the fact that spore formation in the Myxosporidia does not 
terminate the life cycle) and the further fact that, as Biitschli remarks, 
no known myxomycete spore has any structure comparable to the 
1 Ofcourse it may hereafter be found, but it will be time enough to approximate 
the two groups when it is found. 
Evenif its existence were demonstrated (and, from sarcosporidian analogy, Pfeiffer 
regards it only as probable), the process described by Pfeiffer (Die Protozoen als 
Krankheitserreger, 1 ed., 1890, p. 34; 2 ed., 1891, p. 108; see also p. 227) in the 
muscles of the barbel could not possibly bear this construction, as the myxosporidium 
fusion here described is not zoologic, but secondary to common incapsulation, and 
is rather comparable to fusion of abscesses and ovarian cysts, where the adjacent 
walls disappear from pressure-atrophy, or otherwise. 
This fusion process under pressure has also recently been observed by Korotneft 
(see p. 188). 
? This statement must perhaps now be qualified; see pp. 77, 277. 
