190 THE ROYAL SOCIETY OF CANADA 



collect around the periphery and leave the centre free (Fig. 13). 

 The wall of the cyst proper is composed of a firm transparent con- 

 nective tissue which renders the procuring of whole specimens 

 of the contained larvae a matter of considerable difficulty. The 

 latter was seen to be quite active in situ in most cases. 



I have also noticed that the skin of a number of fishes taken in 

 Passamaquoddy Bay, notably Tautogolahrus adspersus (Walb.), 

 Gunner, is greatly infected with small pigmented cysts, similar to 

 those just described, which in all probability would be found to contain 

 larvae of this species: Linton describes the species from the Gunner. 



Species from Fresh- Water Fishes.* 



14. Gyrodactylus médius Kathariner. 7, p. 158. 



On the skin of Micropterus dolomieu Lacépède, Small-mouthed 

 Black Bass. 



A single specimen taken from the dorsal fin of a small bass, 14mm. 

 in length, is referred to this species chiefly on account of its size, 

 0-32 X • 057mm. The large hooks (Fig. 10) in the posterior disc, how- 

 ever, are relatively simpler and larger than in Kathariner's G. médius 

 and G. gracilis, being 0-054 in length. They and the sixteen smaller 

 peripheral hooks, each 0-034 in length, compare more favorably, as to 

 size, with Wegener's description of G. elegans v. Nordm. (28, pp. 

 12-13). 



15. Ancyrocephalus paradoxus Greplin = Tetraonchus unguiculatus 



(Wag.). 28, pp. 18-22. 



On the gills of young M. dolomieu. 



The specimens at hand are all much smaller than those described 

 by Wegener, the largest (curved as in Fig. 11 A) being 1 -0 in length by 

 0- 17 in width. That portion of the worm behind the vitelUne glands, 

 which occupied in the same specimen about 0- 32mm. .of the whole 

 length, is comparatively thin and usually somewhat crenulate laterally 

 (Fig. IIA). The posterior disc of another specimen (Fig. IIB) gave 

 the following measurements: Length, 0-085; width, 0-102; while the 

 pharynx of still another was 0-050 in transverse diameter. In these 

 obviously quite young specimens the chitinous "clamps," two in 

 number, supporting the pairs of hooks, were very small, difficult to 

 see and in many cases apparently absent. The anterior end in every 

 case was much more pointed than that shown in Wegener's figure. 



*The list of monogenetic species should include Diplohothrium armatum F. S. 

 Leuckart (Zool. Bruchstiicke, III Helm. Beitrâge, Freiburg, 1842: 13-18, Fig. 6, 

 Taf. I) which, since the preparation of the manuscript of this paper, I have found 

 on the gills of Acipenser rubicundus Le Sueur, the Lake Sturgeon, from the St. 

 Lawrence River, near Iroquois, Ontario. 



