1132 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 



Farther on we shall have occasion to refer again to Fouquet's inves- 

 tigations and the new family of CUiata established by Saville Kent, and 

 we now return to the infusorian discovered by me. As has already been 

 mentioned, we observed on the skin of various freshwater fishes in our 

 aquarium — principally on the fins and the head, sometimes also on the 

 eyes and on the opercula — very distinct milky-white round spots, whose 

 diameter varied from 0.25 to 0.6 millimeter. Microscopic investigation 

 of these spots showed that they were due to the presence of large in- 

 fusoria, whose form and structure I have endeavored to represent in 

 Fig. 1, drawn from life. These infusoria were found on or in the epi- 

 dermis, and showed between the epidermic cells a very distinct rotating 

 motion, either from right to left or from left to right. Although in most 

 cases a single white spot on the skin of the fish indicated the presence 

 of a single infusorian, 1 observed in some rare cases two, three, or more 

 infusoria imbedded in the epidermis close by ea«h other. The shape of 

 the infusoria was in most cases oval, with a long diameter of 0.615 mil- 

 limeter, iind a short diameter of 0.408 millimeter. The globular indi- 

 viduals, which were much rarer, had a diameter of 0.514 millimeter. I 

 must state, however, that I also obiserved a number of much smaller 

 individuals. 



The body is inclosed in a thin, tender, elastic cuticle, covered all over 

 with very fine cilia, about 0.0046 millimeter in length. The layer below 

 the cuticle is finely granular, with a large number of contractile vacuoles 

 of difl:erent sizes. Even with the aid of the highest powers of the 

 microscope I have not been able to discover any trichocjsts. Even in 

 the live animal the strangely bent nucleus is seen very distinctly shim- 

 mering through the ])lasma of the body (Figs. 1, 2, 3) ; but when the 

 infusoria have been killed by osmic acid (i per cent), and are then 

 treated according to the well-known method of Certes,^^ the horseshoe- 

 shaped nucleus in the largest individuals shows a beautiful red color, 

 and a transverse diameter of 0.139 millimeter (Fig. 4). This nucleus 

 consists of a coarsely granular substance and is enveloped in a very 

 delicate membrane, which appears verj^ distinctly in individuals which 

 for some hours have been kept in a glass (;ell. I have not noticed a 

 nucleolus in any of the individuals examined by me. 



The endoplasm proper contains a large number of granules and par- 

 ticles of different size; and in most individuals — and this is important — 

 there may be observed very distinctly larger or smaller heaps of pig- 

 ment granules which show a very striking resemblance to the granules 

 found in the pigment cells and chromatophores of the epidermis of fish. 

 The plasmic contents of these infusoria at any rate contained many 

 small particles, which, as I suppose, can only have entered the endo- 

 plasm from without. This supposition was confirmed by the discovery 

 of a very distinct oral opening with a well-developed gullet, which was 



'^A. Certes : ' ' Sur une m^thode de coriservation dea Infusoires," in Compt. Bend, Ac. de Sc 

 Paris, 1871), vol. 88, pj]. 433-436. 



