178 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



W. Saville Keiit (1880-82, vol. I, p. 109) refers to Ichthyophthirius miiltiJilUs, and 

 creates (vol. n, p. 530) for it a new family, Ichtliyophthiriidce S. K., with the diag- 

 nosis : — 



Animalcules adherent, more or less ovate, ciliate throughout, oral cilia of larger size than those 

 of the general cuticular surface, oral region adhesive, acetabuliform. 



Saville Kent (vol. n, p. 531) seems to doubt the absence of a mouth because of the 

 presence of black substance in the body and also upon other grounds. (Cited from 

 Kerbert). 



Kerbert (1884)* noticed a skin-disease on several of the fresh- water fish (see list 

 of hosts, p. 175) of the Amsterdam Aquarium, caused by an infusorian parasite, which 

 he thought was probably identical with the form described by Fouquet, but for which, 

 on account of certain apparent differences in structure, he created a new genus and 

 new species, Chromatophagus parasiticus, which he places in Saville Kent's family 

 Trachelocercidce. This disease has been termed "spotdisease" (Flecken-Krankheit), and 

 should not, according to Kerbert, be confounded with the disease " Pocken- Krankheit 

 or pox," observed by Wittmack in various cyprinoids, where, "on the surface of the 

 skin, there appear bluish-gray spots of a slimy, fungus-like character, which spread 

 more or less over the entire bodv. and extend to the eves, fins, etc." Kerbert never 

 discovered any infusoria in pox, although Wittmack thinks the cause of the disease 

 may possibly be traced to them. Spot disease, according to Kerbert, also occurs on 

 salt-water fishes, but the ciliated parasite he found upon Mustelus vulgaris Mull. & 

 Henle, and Ac.anthias vulgaris Eisso, in the pulp cavity of numerous placoid scales, is 

 probably not the same as the form he found upon the fresh-water fish, although Kerbert 

 simply states that the rapid decay of the fish prevented him "from making a thorough 

 examination of this species of infusorians." 



Kerbert then discusses the views of Hilgendorf and Paulicki, and Fouquet, at some 

 length. He, agreeing with Saville Kent, looks upon the dark granules in the infusoria 

 as the remains of cutaneous pigment of the fish, and hence as positive proof against the 

 view that these parasites have no mouth. Hementions a paper by Livingston Stone, t 

 in which a cutaneous parasite of Salmo fario is described and figured, which Kerbert 

 thinks is probably a rotifer rather than an infusorian. According to Kerbert also, La 

 Valette St. George refers to the articles of Hilgendorf and Paulicki (1809) and Stone, but 

 makes no further statements. As Kerbert's paper appeared in full in the Fish Com- 

 mission report, it will suffice here if the barest outline of his results is given. The para- 

 sites measured 0*015 mm by 0-408 mm ; no trichocysts could be distinguished; mouth 

 was lateral in position; pharynx was well developed; anus absent but the fieces were 

 seen to escape from various points of the body. Reproduction not by fission, but essen- 

 tially the same as described by Fouquet, the division always taking place in the dark. 



Biitschli (1887) considers that the parasites found by Hilgendorf and Paulicki, 

 Fouquet, and Kerbert are identical. He does not consider that Ichthyophthirius 

 should rank as a genus, but makes a subgenus of it in the genus Holophrya Ehrbg., 

 1831, (subfamily) \Holophryina Perty, 1852 (Fam.) emend., family %Enchelina (Ehrbg.) 



* As Kerbert's original is not at my disposal, I quote from Kerbert 1885 and 1886. 

 tDomesticated trout: How to breed and grow them. Third ed. ; Cliarlestown, N. H., 1877, p. 277. 

 (Appendix I.) 



XHolophryinw, according to the rules of the International Zool. Congress. 

 § Enchelyidce, according to the rules of the International Zool. Congress. 



