106 REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 



ORGANAL DISTRIBUTION. 

 ORGANAL DISTRIIUTTION OF THE GrENERA AND SPECIES. 



Perugia^ remarks that there is a marked dittereuce in seat between 

 the Myxosporidia of marine and tliose of fresh-water fislies. In marine 

 fishes they occur principally in the gall bladder, while in fresh-water 

 fishes their organal range is much wider. The finding of cysts on the 

 brancliijE of the marine genus Mufjil (see p. 213) rather corroborates 

 than contradicts this view, inasmuch as these fishes ascend rivers for 

 along distance, and those which yielded the myxosporidian cysts also 

 yielded a Trematode of a genus i)eculiar to fresh-water fishes, viz, Tetra- 

 onchuH vanhenedenii Par. & Per. 



The organal distribution of the MiixoHporUlUi is very extended. The 

 following points are of special interest, and (comprise the iirincii)al 

 anomalies of distribution not covered by the tables below. 



Nervous system. — "NTo species have ever been reported. 



Testicle. — No species have ever been reported, a fact which,^ consid- 

 ering their frequency in the ovary, is very surprising (cf. the presence 

 of ^^ Mi/xosporidium'''' hryozoides on the spermatoblasts of Alcyonella 

 J'imgosa; see p; 187). 



Superficial tract. — General similarity of conditions, histologic struc- 

 ture, and fauna justify the fusion of the general surface, skin, scales, 

 the branchife, the eye, and the air bladder into one tract. The charac- 

 teristics of this tract are principally the i)redominance of connective 

 tissue, and (?) a relatively larger sui)ply of oxygen (see p. 224). 



Air bladder: Only two species are known from this seat. Both of 

 these occur in Cyprinida\ in which the bladder communicates freely 

 with the intestine, and hence presumably contains oxygen. This fact, 

 the histologic similarity, and the fauna suggest very strongly the pro- 

 priety of including the air bladder in the external tract. The species 

 are Gen. incert. sp. 15 and Myxobolus ellipsoides. 



Intestinal canal. — They would appear to be very rare here. I am not 

 aware that any sj^ecies has ever been reported from the lumen, the 

 nearest approach to it being one {Myxidiumf sp. 102) from the bile- 

 ducts. And yet such a species as the last must almost certainly find 

 its way into the intestine; probably, however, as separated, single 

 spores, very difiicult to find. In addition, Myxobolus elU2)soides and 

 M. sp. 51 (the latter from the wall), and finally Gen. incert. sp. 17 

 (which, however, may or may not be myxosporidian) occur on, or in the 

 intestine.^ 



'Boll. Scientif., Pavia, 1890, xii, p. 139. 



-As remarked by Th^lohan (Auual. de Microgr., 1890, il, p. 197). 



3The fact that M. ellipsoidi's aiul M. xp. 51 are, of all the Mfixosporidta, the species 

 haviug the widest organal distributiou, should not be lost sight of iu cousideriug 

 their presence iu unusual seats. 



