530 ORDER HOLOTRICHA. 



HAB. Salt water ; movements smooth and even, or rotating on its long 

 axis. 



The general contour of this species, as recently figured and described by Cohn,* 

 closely resembles that of the fresh- water type Loxophyllum meleagris. 



Loxophyllum setigerum, Quenn. 



Body flattened, irregularly rhomboidal, widest centrally, most attenuate 

 anteriorly ; the dorsal border nearly straight, neither undulate nor bearing 

 trichocysts, the ventral one strongly and gibbously arcuate, three or four 

 seta-like structures projecting irregularly from its posterior half; contractile 

 vesicles numerous, forming a continuous row down the dorsal margin. 

 Endoplast moniliform. Length 1-150". HAB. Saltwater. 



Fam, VIII. ICHTHYOPHTHIRIID.2E, S.K. 



Animalcules adherent, more or less ovate, ciliate throughout, oral cilia 

 of larger size than those of the general cuticular surface, oral region 

 adhesive, acetabuliform. 



GENUS I. ICHTHYOPHTHIRIUS, Fouquet. 



Animalcules more or less ovate, highly elastic, entirely ciliate, oral 

 orifice terminal, situated in the centre of an adherent, discoidal, acetabuli- 

 form area, the inner margin of which bears numerous inwardly projecting, 

 setose cilia. Endoplast and contractile vesicles conspicuously developed. 

 Occurring as parasites on the epidermal surface of various fishes. 



Ichthyophthirius multifiliis, Fouquet. PL. XXXII. FIGS. 1-8. 



Body subglobose or ovate, flexible and elastic ; cuticular surface finely 

 and evenly ciliate throughout, the cilia arranged in fine, intercrossing, 

 obliquely parallel rows ; an aspect as of trichocysts underlying the entire 

 cuticle apparent in the younger zooids ; adhesive suctorial disc apical, 

 minute, and cup-like, its inner surface bearing about twenty, inwardly 

 radiating, larger, setose cilia ; contractile vesicles numerous, minute, scat- 

 tered throughout the cortical layer ; endoplast band-like, curved ; endoplasm 

 densely granulate. Length 1-150". 



HAB. Parasitic on the common Trout, Salmo trutta, and other soft- 

 skinned fresh-water fish. 



The occurrence of this animalcule as a parasite of various fresh-water fish, in 

 eluding more notably the Loach, Cobitis fossilis, was notified by MM. F. Hilgendorf 

 and A. Paulicki of Hamburg, in the ' Centralblatt ' for January 1869. The account 

 then given of it was, however, very incomplete, and the animalcule was pro- 

 visionally referred to Ehrenberg's genus Pantotricha. The first full description of this 

 type, accompanied by the bestowal upon it of the distinctive title above given, did 

 not appear until some years later, when M. Fouquet figured and described it at 

 length in the ' Archives de Zoologie Expe'rimentale,' torn. v. pp. 159-165, for the year 

 1876. According to thfs authority, the species had then for the last ten years proved 

 very destructive to the young trout raised in the artificial basins of the fish-houses 



* " Neue Infusorien im Seeaquarium, " ' Zeit. Wiss. Zool.,' Bd. xvi., 1866. 



