66 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 
results may be obtained here. Obviously the first step in work of this 
kind is the collection of facts, especially those bearing upon the parasite, 
its nature, life-history, intermediate hosts, enemies, and its connection 
(whether causal or otherwise) with diseases or other morbid processes 
in its host. Such data are a necessary preliminary to preventive or 
curative measures. 
The present paper is a contribution toward the object indicated. A 
few words now as to its scope. The attempt has been made to compress 
theentire literature (as far as possible, every known fact) into one article. 
Further, every form ! which has been at any time definitely referred to 
the group is here included. Such collection of forms necessarily involved 
the exercise of some judgment as to specific identities and distinctions. 
As most of the known species are available only in the form of descrip- 
tions, usually very meager, and of drawings which, especially the older 
ones, represent only the most general features,’ it is hardly reasonable 
to hope that any first attempt at compilation of the synonymy will 
prove satisfactory in all respects. Still in many cases the synonymy 
is fairly well established. 
The main guide in the correlation of the described forms has been 
identity of host andseat. Of course it is not contended that this proves, 
but merely that it more or less strongly suggests, identity of parasite. 
The confirmatory test is naturally a comparison of figures and descrip- 
tions. This latter test will of course be preferred to the test by iden- 
tity of seat as soon as we shall be in the possession of sufficiently 
accurate and detailed descriptions and figures, but in the present state 
of our knowledge the mere absence of difference between more or less 
incomplete descriptions and figures of two forms with different habitats, 
produces no conviction in my mind of the identity of the forms. In gen- 
eral it is only where a double correlation (of host and seat on the one 
side, and of descriptions and drawings on the other) has been possible, 
that different forms have been united. In other words, the presump- 
tion throughout has been in favor of distinctness. From this fact it may 
be expected that future investigation will tend to reduce somewhat the 
number of forms here recognized. 
The nomenclature has been compared and revised, and for all recog- 
nizable species binomial names have been substituted for the clumsy 
circumlocutions “psorosperms of the pike,” etc., formerly in use. It 
may perhaps be thought that in my preliminary paper and in the present 
1 Although it has been my aim to include in this paper descriptions and figures of 
all forms ever definitely referred to the Myxosporidia, the species noted on pp. 135- 
137 have been omitted. 
2Tt must be further noted that hardly one of the older writers regarded these torms 
from ataxonomic standpoint. Their principaldesire was to work out the life-history 
and affinities of the group rather than of the individual species; and they seem to 
have observed the latter mainly for the light they shed upon the life-history of 
the group as a whole, contenting themselves with designating the different forms as 
‘psorosperms of the pike,” etc. 
