GENUS ICHTHYOPHTHIRIUS. 53 I 



of the College de France, the inflammation of the epidermal tissues induced by their 

 presence in large quantities proving fatal within a very short inteiTal. In a 

 fish affected by these parasites, prominent, rounded, milk-white spots are to be 

 observed on the eyes, fins, branchiae, or general cuticular surface, in depressions 

 in which, when examined with the aid of the microscope, the animalcules will 

 be found lodged, sometimes singly and in other instances in great numbers. Each 

 animalcule is fixed to the bottom of the depression by the apical adhesive disc, and 

 rotates backwards and forwards from right to left and left to right upon its longitu- 

 dinal axis, by the movement apparently of the cilia of the cuticular surface, and thus 

 bores it way deeper into the skin of its victim. The reproductive phenomena of this 

 species, as recorded by Fouquet, are highly interesting. Arriving at maturity, the 

 animalcules become detached from their host, and falling to the bottom of the water, 

 encyst and become divided by repeated segmentation, accompanied by a like division 

 of the endoplast, into a morula-like mass consisting of at least a thousand ovate 

 ciliated bodies which ultimately escape from the ruptured cyst, and grow by degrees 

 to the parent form. This reproductive process occupies an interval of from forty to 

 fifty hours. At first, the young animalcules thus developed, PI. XXXII. Figs. 5 and 6, 

 are much more elongate than the parent zooids, and have no apical suctorial disc ; 

 the endoplast is likewise simply ovate, and accompanied by an endoplastule which 

 disappears a little later, while the contractile vesicle is single and laterally developed. 

 The close correspondence of this form of multiplication with the sporular reproductive 

 process of the simpler Flagellata is eminently noteworthy. The two or three months 

 extending from the end of May till August are those in which the young trout are 

 most liable to be affected by the attacks of this Infusorium. The placing of frag- 

 ments of tiles or other substances against which the fish can rub themselves, and 

 thus get rid of their puny assailants, supplemented by the maintenance of the water 

 at a low temperature, are recommended as the best checks to their inroads. 



Some uncertainty would seem to exist respecting the precise import of the 

 suctorial organ developed at the apical extremity of Ichthyophthirius. According to 

 Fouquet, this structure does not constitute a perfect oral apparatus, it consisting 

 merely of a circular opening, bordered by larger cilia, which leads into a small 

 cul-de-sac, and is not continued into the deeper substance of the body. Carmine 

 administered in a pulverized condition was not assimilated, a circumstance, correlated 

 with the structural peculiarities just cited, Fouquet considers sufficient to indicate 

 that the animalcule is strictly mouthless, and that the apical acetabuliform organ, 

 while possibly representing a degraded oral aperture, is subservient merely for the 

 purposes of adhesion. Viewed in this light, the animalcule is regarded as possessing 

 probable affinities with the Opalinidae, in which group, indeed, one genus, Hap- 

 tophrya, is distinguished by its possession of a somewhat analogous acetabuhform 

 organ. It is at the same time worthy of remark that the densely granular character 

 of the endoplasm of Ichthyophthinus, as indicated by Fouquet's figures — certain of 

 which are further distinguished by the incorporation of so-called pigmentary cor- 

 puscles — is highly suggestive of the presence of extraneously derived solid nutriment. 

 To this it may be added that all mouthless organisms, in the strict sense of the term, 

 are, so far as known, essentially endoparasites, subsisting by absorption on the 

 nutrient juices provided within the intestinal viscera of the hosts they respectively 

 inhabit. Under these circumstances it has been considered advisable to at least 

 provisionally retain the present highly interesting type among the ordinary Stoma- 

 tode Holotrichous Ciliata, apportioning it there, with reference to its remarkable 

 oral or pseud-oral system, an independent family distinction. 



Fam. IX. OPHRYOGLENIDiE, S. K. 



Animalcules free-swimming-, ciliate throughout, oral and cuticular cilia 

 uniform in size ; oral aperture terminal, lateral or ventral, situated at the 

 bottom of a distinct oral fossa or vestibulum, within which is enclosed a 

 vibratile flap or membrane. 



