SEA-FISHERIES LABORATORY. 293 



shewed that parasites such as myxosporidia were absent. 

 The gills were then examined, and these were found to be 

 pale and not in a very healthy condition; also small, 

 rounded white specks could just be seen with the naked 

 eye, and when these were examined in detail they were 

 seen to be ciliated infusorians. Fig. 4, pi. VIII, 

 represents one of these organisms. They varied greatly 

 in size, the largest being about 0'75 mm. in length and 

 0*47 in breadth, and the smallest about 0'3 x 0*28 mm. 

 Usually they were oval in shape, but some were quite 

 round. Their numbers were not considerable ; in a small 

 piece of gill, from one of the smaller fishes, which was 

 stained and mounted whole there were 17 parasites. 

 There were 30 double filaments in this piece of gill. 

 In some other pieces of gill roughly examined the 

 parasites appeared, however, to be more abundant than is 

 stated above. They lie in the gill between the filaments 

 and compressed by the latter. They were also found on 

 the internal walls of the operculum and branchial cavity. 

 The parasite is completely covered by fine cilia. The 

 nucleus is situated towards one end, or near the middle of 

 the body, and is large and horse-shoe shaped. It is very 

 coarsely granular. The mouth is situated at the opposite 

 end and is small and very definite in outline. A faint, 

 longitudinal striation may be observed in the body. 

 Round the margin, or rather underneath the cilia, is an 

 evident cortical layer. Small vacuoles are very numerous 

 in some specimens. 



All these characters are those of Ickthyophthirius 

 multifiliis, Fouquet, and I have no hesitation in thus 

 identifying the creature. It is a skin parasite, which has 

 been described as infesting 28 or 30 species of 

 fresh-water fishes in the rivers and lakes of Germany, 

 France, Holland and the United States of North 



