200 THE ROYAL SOCIETY OF CANADA 



and opaque-white, Y-shaped excretory system, which latter, as in 

 Crepidostomum laureatum, does not seem to communicate with the 

 exterior for some time. In fact my study of these early appearances 

 of the excretory system, in fresh as well as in preserved material, 

 leads me to agree with Osborn in his suggestion that "the process is 

 one of storage during encystment as a mode of disposal of the waste 

 products pending the liberation of the worm." A much smaller cyst, 

 containing two distinct eye-spots but no indications of the forked 

 excretory vesicle among the mulberry-like mass of amoeboid cells, 

 was perhaps a yet earlier stage. On the other hand, the largest 

 cysts (Fig. 20) contain much larger worms, quite active in situ, es- 

 pecially when stimulated by a little pressure, in which there are to be 

 seen, besides the well-developed excretory vessels, the oral sucker, 

 pharynx, oesophagus, intestinal coeca and the beginnings of the two 

 ventral suckers and of the reproductive organs (Fig. 21). No mature 

 worms were taken from cysts. The only cyst found in Not. hudsonius 

 was located in the muscles near the caudal fin of a 28mm. specimen, 

 while one only was found in the muscles of an adult Sunfish. The 

 smallest Rock Bass found to contain the cysts was 18mm. in length. 



Although the distribution of these young and encysted stages was 

 pretty thoroughly studied, no experiments were carried out for the 

 purpose of finding out how the very earliest stages, whatever they 

 may be, obtain entrance to the young Bass. Two possibilities suggest 

 themselves, namely, that they enter directly from the outside by 

 piercing the skin and boring their way into the muscles, which would 

 account for their encystment in these structures, or they are carried 

 by the blood stream from the stomach and intestines, into whose walls 

 they may pass after coming in with the food, to the farthest points of 

 the body, for instance the muscles at the base of the caudal fin. On 

 account of most of them being situated in the muscles along the 

 sides of the body and on the head, I am inclined to the former sug- 

 gestion, which, however, I am unable to support by any further facts. 

 27. Gasterostomum pusilliim Stafford. 26, pp. 494-95. 



In stomach, intestine and coeca of young M. dolomieu, and 

 intestine of Boleosoma nigrum. 



The measurements of two of the largest specimens, respectively 

 from the intestine and pyloric coecum of young Bass, are as follows: 

 Length, 0-45, 0-68; width, 0-154, 0-172; diameter of anterior sucker, 

 0-120, 0-137, of oral sucker, 0-051, 0-051. Although these do not 

 closely agree with those given by Stafford, I am inclined to refer the 

 worms to this species, at least tentatively, owing to the fact that most 

 of them are immature, only a few being found to contain eggs. The 

 latter in a much collapsed condition when in oil of cedar were 0-042 



