[7] CHROMATOPIIAGUS PARASITICUS. 1133 



always fouud iu a soniewliat lateral position at tlie anterior iiole of the 

 body. This oral opening (Fig. 1) is circular, surrounded by an annular 

 thickening of the cuticle, and has, according to the size of the indi- 

 vidual, a diameter of 0.025 to 0.04 millimeter. The annular thickening 

 of the cuticle which surrounds the oral opening proper bears a wreath 

 of somewhat longer and stifier cilia than are fouud on the rest of the 

 surface of the cuticle. 



The length of the gullet is about 0.02 millimeter, and its diameter 

 about 0.01 millimeter. The inner end of the gullet, which is directed 

 toward the endoplasm of the body, was slightly bent. Its entire inner 

 surface is covered with long, active cilia, the free ends of which are 

 directed toward the oral opening and protrude a little beyond it. These 

 infusoria have no well-defined opening serving as an anus, and, as I have 

 very distinctly observed, the fex?es are expelled from various parts of 

 parts of the body. 



After having given ray observations on the structure of these in- 

 fusoria, I must call attention to the shape of the body, or rather to 

 the extreme variability of its form, in the individuals which have been 

 removed from the epidermis of the fish. If the infusoria are put in 

 a glass vessel, the shape of the body of the different individuals shows 

 such great differences that at first it seems hardly possible that they 

 belong to one and the same species. The body appears to be extremely 

 metabolic (Fig. 2). Folds, emarginations, and projections appear in 

 one place and disappear in another ; so much so that one feels inclined 

 to think that the organism is not an infusorian but an amoeba. In 

 fact, I once observed an individual (Fig. 3) that was retort-shaped and 

 had a neck, at the free end of which the oral opening and the gullet 

 could be distinctly recognized. 



In conclusion, I must discuss more fully the propagation of these 

 infusoria. From the beginning of my observations it struck me that 

 the individuals that, for the purpose of closer examination, were re- 

 moved from the epidermis of the fish never showed the slightest in- 

 indication of the process of fission ; and any other mode of reproduc- 

 tion of these infusoria living in the epidermis seems hardly possible. 

 During my observations conducted in the daytime I have never noticed 

 the phenomenon of fission. I consequently arrived at the supposition 

 that possibly propagation by fission might take place during the even- 

 ing, or even during the night, on the epidermis of the fish. I therefore 

 examined tho infusoria removed from the epidermis for several hours 

 after sundown, constantly taking new individuals from the epidermis 

 and subjecting them to a very thorough examination under artificial 

 light in Engelmann's live-box. The result, however, was a negative 

 one, and no sign of a process of fission could be detected. In order to 

 convince myself whether such a process actually took place by night, 

 on March 16 and 17 I took from a Tinea vulgaris Cuv., to which a large 

 number of infusoria adhered, some infusoria every hour of the night, 



