DISTRIBUTION OF CLINOSTOMUM MARGINATUM. 355 



of getting some information which would lead up to the discovery 

 of the first host. The only forms on which I recognized the 

 parasites were the bass and the perch. Other fishes which were 

 investigated with wholly negative results were the grass-pike, 

 which is very often caught there, and the sun fish, Eupomotis 

 also very common. Various gasteropods and insects were 

 examined but without any result. I have thus far not been able 

 to obtain any clue to the source of infection of the fish. 



The percentage of infected individuals found among the bass 

 was very great. I do not happen to have any statistical data 

 bearing on this point, but the parasite was found in nearly every 

 bass submitted to examination, while in the perch it was much 

 more rare. The cysts were very easily seen, being large, opaque 

 and very creamy white, in marked contrast with the darker 

 semi-translucent muscular tissue in which they lie imbedded. 

 When the fish were skinned in preparing them for cooking the 

 cysts walls were often torn open and the conspicuous worm seen 

 moving on the surface of the meat. The cysts were found in all 

 parts of the lateral muscles, deep and superficial, dorsal and 

 ventral and headwards and tailwards. There was no evidence 

 from their location bearing on the question of the mode of entry 

 which had been adopted by the worms, but the observations of 

 various others who have reported the worm from the gills, roof 

 of mouth, branchiostegal membranes and pectoral fin would 

 indicate that the worm enters the fish in the head region. If so 

 it is difficult to imagine how they reach the places where we find 

 the cysts if they are as large as we find them when they enter. 

 On the other hand, if they enter as small and immature stages 

 we should surely be able to find some evidence of it. Some of the 

 worms should be less fully developed than others, or some of the 

 waste products of the chemical processes involved in growth 

 should be recognizable. So that we are unable to find a solution 

 to this problem with the data at present available. 



The number of cysts in single individuals varied greatly. The 

 minimum number found was seven and the maximum number 

 was more than one hundred. The appearance of one of the cysts 

 in situ in the muscle is shown in Fig. 2. They are oval or spher- 

 ical. They are smaller than those reported by Looss ('85) from 



