66 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



results may be obtained here. Obviously the lirst stey) in work of this 

 kind is tlie collection of facts, especially those bearing' upon the parasite, 

 its nature, life-history, intermediate hosts, enemies, and its connection 

 (Avhether causal or otherwise) Avith diseases or other morbid processes 

 in its host. Such data are a necessary prcliminiiry to preventive or 

 curative niea sures. 



The present paper is a contribution toward the object indicated. A 

 few words now as to its scope. The attempt has been made to comi)ress 

 theentire literature (as far as possible, every known fact) into one article. 

 Further, every form ' which has been at any time delinitely 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 comi»ilation of the synonymy will 

 prove satisfactory in all resj^ects. 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 and seat. Of course if is not contended that this proves, 

 but merely that it more or less strongly suggests, identity of parasite. 

 The confirmatory test is uaturally 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 descrii)ti()ns and figures of two forms m ith 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 sjiecies 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 



' Altlioiigli it lias been my aim to include in tliis ])aper dcscriptious and figures of 

 all forms ever definitely reftirred to the Muxoxporldia, tlie epecies noted on pp. 135- 

 137 have been omitted. 



-It must be further noted that hardly one of the older writers regarded these lorms 

 from a taxonomic standpoint. Their principal desire was to work out the life-history 

 and affinities of the grouji 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 difl'ercut forms as 

 " Dsorosperms of the pike, " etc. 



