THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 275 



viz : (1) That bisporogeuesis must be admitted as a (very striking) generic 

 feature; and (2) that if, as Perugfa asserts, Myxoholus merlucii possesses 

 this character, it is in all probability a Ceratojnyxa, and not a, Myxobohts. 

 And two facts confirui this latter view, viz:' The improbability in Myxo- 

 holus of a gall-bladder habitat and the rarity of spores whose breadth 

 exceeds the length. Perugia's species is, however, provisionally left 

 under Myxoholus, on account of his positive statement as to the presence 

 of an iodiuophile vacuole. 



The following is an abstract of Thelohan's paper: 

 ^^ ,„ Besides the species fornieiiy published ' iu which the mvxosporidium 



L o - J produces but 2 siiores, I have since confirmed the s;ime peculiarity iu a 

 rather large number of new forms in the gall-bladders of certain Mediterranean fi.shes. 

 All these 2-8poring species belong to ii y family " Myxidi^es," the greater part of them 

 being clearly referable to Ceratomyxa, while the others, by successive moditicatious 

 of spore-form, establish a transition between that genus and Splucrospora. This 

 last connects the 2-sporing species with the many-sporing, and at the same time, by 

 its habitat, the free species to the tissue-imbedded forms. 



There is thus no absolute separation between the 2-sporing and the other Myxospo- 

 ridia. The 2-sporiug always live a free amoeboid life in the bile-fluid and exhibit a 

 very great motility, owing to specialized pseudopodia heretofore described. 



These 2-sporing Myxosporidia with localized pseudoitodia and rapid movements 

 represent the most elevated type of organization. As regards the interpretation of 

 the facts, are they perfected types derived from inferior, or are they 

 '- ' * -' the primitive type, the others, especially the tissue- imbedded species, 



being forms degraded by a more pronounced (a, so to speak, more intimate) parasit- 

 ism ? Th61ohan favors the latter view. Great stress is to be laid upon the pro- 

 gressive increase in the number of spores occurring pari passu with degradation 

 of form and increase of parasitism, such increase of reproductive elements being 

 always one of the most constant attributes of parasitism. 



84. Ceratomyxa arciiata Th^lohan, 1892. 



Compt. Rend. Acad. Sci. Paris, cxv, p. 1091. 



Cyst none. 



Myxosporidmm. — Of variable form, diameter apparently not exceed- 

 ing 35 or 40 /i; destititte of prolongations. Endoplasm finely granular 

 and homogeneous, containing some scattered fatty globules; destitute 

 of sijherules. Pseudopodia ectoplasmic, lobed; the filiform variety 

 absent. 



Spore. — Eelatively very small; length, 5 //; breadth, 40 //. 



Hahitat. — Gall-bladder of Onus tricirratus {=Motella tricirrata) col- 

 lected at Koscoff, in August, 1892. 



Bemarlis. — This diflers from the other species of the genus princi- 

 pally in its much smaller size. 



85. Ceratomyxa agilis Thdlohan, 1892. 



Compt. Rend. Acad. Sci. Paris, cxv, pp. 962-3. 



Myxosporidium. — Attaining a maximum length of 85 ;/, and a maxi- 

 mum breadth of 20 /Y ; assmning various forms, most frequently elong- 

 ated, subcylindric, a little swollen at the middle. One end (which on 

 account of being constantly foremost in progression is to be regarded 



"Compt. Rend. Acad. Sci. Paris, 1894, cxviii, pp. 428-430. 



