THE MYXOSPORIDIA, OR PSOROSPERMS OF FISHES. 219 
viz: (1) That bisporogenesis must be admitted as a (very striking) generic 
feature; and (2) thatif, as Perugfa asserts, Myxobolus merlucii possesses 
this character, it isin all probability a Ceratomyxa, and not a Myxobolus. 
And two facts confirm this latter view, viz: The improbability in Myxo- 
bolus of a gall-bladder habitat and the rarity of spores whose breadth 
exceeds the length. Perugia’s species is, however, provisionally left 
under Myxobolus, on account of his positive statement as to the presence 
of an iodinophile vacuole. 
The following is an abstract of Thélohan’s paper: 
Besides the species formerly published! in which the myxosporidium 
produces but 2 spores, I have since confirmed the same peculiarity in a 
rather large number of new forms in the gall-bladders of certain Mediterranean fishes, 
All these 2-sporing species belong to:my family ‘‘ Myxidiées,” the greater part of them 
being clearly referable to Ceratomyxa, while the others, by successive modifications 
of spore-form, establish a transition between that genus and Spherospora. 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-sporing always live a free amceboid life in the bile-fluid and exhibit a 
very great motility, owing to specialized pseudopodia heretofore described. 
These 2-sporing Myxosporidia with localized pseudopodia 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 
gee 230) 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? Thélohan 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. 
[Page 429] 
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84. Ceratomyxa arcuata Thélohan, 1892. 
Compt. Rend. Acad. Sci. Paris, cxv, p. 1091. 
Cyst none. 
Myxosporidium.—Of variable form, diameter apparently not exceed- 
ing 35 or 40 yw; destitute of prolongations. Endoplasm finely granular 
and homogeneous, containing some scattered fatty globules; destitute 
of spherules. Pseudopodia ectoplasmic, lobed; the filiform variety 
absent. 
Spore.—Relatively very small; length, 5 4; breadth, 40 
Habitat.—Gall-bladder of Onus tricirratus (=Motella tricirrata) col- 
lected at Roscoff, in August, 1892. 
Remarks.—This differs from the other species of the genus princi- 
pally in its much smaller size. 
85. Ceratomyxa agilis Thélohan, 1892. 
Compt. Rend. Acad. Sci. Paris, cxv, pp. 962-3. 
Myxosporidium.—Attaining a maximum length of 85 yu, and a maxi- 
mum breadth of 20 4; asswning 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 
1Compt. Rend. Acad. Sci. Paris, 1894, cx vi, pp. 428-430. 
