106 REPORT OF THE COM^IISSIONER OF FISH AND FISHERIES. 

 ORGANAL DISTRIBUTION, 

 ORGANAL DISTRIBUTION OF THE GENERA AND SPECIES. 



Perugia 1 remarks tliat there is a marked difference in seat between 

 the Myxosporidia of marine and those of fresh-water fishes. 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 

 branchiae of the marine genus Mugil (see p. 213) rather corroborates 

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

 a long distance, and those which yielded the myxosporidian cysts also 

 yielded a Trematode of a genus peculiar to fresh-water fishes, viz, Tetra- 

 oncJms vanhencdcnii Par. & Per. 



The organal distribution of the 3fyxosporidia is very extended. The 

 following: points are of special intei-est, and comprise the principal 

 anomalies of distribution not covered by the tables below. 



Nervous system. — No 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 '■'■ Miixospnrid'mm'''' hryo^oides on the spermatoblasts of Alcyonella 

 fungosa; see p. 187). 



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

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

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

 teristics of this tract are principally the predominance of connective 

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



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

 these occur in Cyprinidce, 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 in(;luding the air bladder in the external tract. The species 

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



Intestinal canal. — They would ai^iiear to be very rare here. I am not 

 aware that any species 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 difficult to find. In addition, Myxol)olns ellipsoides and 

 31. 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. 



2 As remarked by Thdlobun (Aiinal. de Microt^r., 1890, ii, p. 197), 



^The fact that M. cllijifioides nnd AF. sp. 51 are, of all the Myxosporidia, the species 



having the widest organal distribution, should not be lost sight of iu considering 



their presence in unusual suats. 



