[cooper] TREMATODES FROM MARINE FISHES 187 



is led to conclude that if the larval stages, possibly the miracidia, do 

 not penetrate from the outside (vide infra, under several species 

 encysted in fresh-water fishes) they are distributed from the stomach 

 and intestines, where they may find entrance to the tissues, to other 

 parts of the body by the blood stream. In support of the latter and 

 more probable hypothesis the position of a particular specimen was 

 quite significant. It was found in the haemal arch of one of the 

 vertebrae near the caudal fin of a small fish, with its anterior end 

 protruding laterally into the muscles. It was an adult, since the 

 uterus was filled with eggs, and had evidently developed in situ, for 

 it was considerably constricted anterior to the acetabulum by the 

 haemal arch whose aperture was much smaller than the diameter of 

 the worm. The dorsal aorta of the host was all but obliterated at 

 this particular level! 



From the small size of both encysted and free individuals, as 

 compared with the measurements given by Stafford, this must be the 

 small variety mentioned by him as occurring in the Salmon. In 

 some specimens the acetabulum was twice as large as the oral sucker. 

 9. Hemiurus appendiculatus Rud. 24, p. 960; 22; 25, pp. 399-401. 



Stomach of Osmerus mordax (Mitchill), Smelt; encysted in body 

 cavities of free-swimming Copepoda. 



The former lot consisted of only five very small specimens of the 

 same size as those from the copepods, excepting the largest, the only 

 one which contained eggs, which was about 0-68 long and 0-19mm. 

 broad just behind the acetabulum. An average example from the 

 second lot gave the following measurements: Length, 0-56; width 

 behind acetabulum, 0-137; diameter of oral sucker, 0-077, of ventral 

 sucker, 0-086. From these data, which although they are from a 

 contracted specimen, agree sufficiently with those given by Pratt 

 (22, p. 355) to warrant the reference of the worms to these species, 

 especially in conjunction with the general appearance and disposition 

 of the reproductive organs, it will be seen that the acetabulum is not 

 twice the size of the oral sucker as Linton records in many places for 

 the adults, but almost equal to it, a fact which Pratt's measurements 

 (0-08 and 0-053, respectively) indicate and which is mentioned in 

 Stafford's description of D. pelagicum Staff., the latter writer, however, 

 giving no measurements of the suckers. Eggs from the uterus of the 

 mature specimen from the stomach of the Smelt averaged 0-020X 

 • 009, the true measurements being probably a little larger than this, 

 since the shells were much contracted and only the inner protoplasmic 

 contents could be clearly seen. The vitelline masses showed in cleared 

 material some tendency towards lobulation. 



