56 American Fisheries Society 



waters of the coast farther south. At Beaufort, N. C, I 

 found this species of cestode which is represented by the 

 flesh parasite of the butterfish, the encysted stage, very 

 abundant in the submucosa of many species of fish, and 

 the adult in two species of shark other than the hammer- 

 head, which has thus far proved to be its most usual final 

 host. There is much reason for thinking, therefore, that 

 the chances of infection are many times greater in the 

 latitude of Beaufort than they are off the New England 

 coast. The method of infection, especially where many 

 cysts occur in the flesh, may be easily inferred, when it 

 is remembered that the ripe, egg-containing joints of the 

 adult worm, living in the intestine of a shark, continue 

 active for a long time in sea water, and when discharged 

 in the water along with the faeces of their host, would 

 be greedily eaten by small fish. A single ripe joint may 

 contain many hundreds or even thousands of eggs. Each 

 of these eggs, when once it is swallowed by a fish, may 

 ultimately become an encysted larva. Thus in the ex- 

 treme case of parasitism of the small fish examined in 

 September, 1911, noted above, it is probable that the 

 school to which they belonged, happened to be in the near 

 vicinity of a shark, most likely a hammerhead, at the 

 time when a considerable number of ripe joints were 

 discharged into the water. The frequent possibility of 

 such happenings will be understood when it is recalled 

 that the chyle in the spiral valve of sharks is often lit- 

 erally swarming with the free joints of these small tape- 

 worms, each of them being the bearer of a large num- 

 ber of eggs. 



CONCLUSION. 



There does not appear to be evidence of any marked 

 periodicity in the occurrence of helminth parasites of 

 marine fishes, either adult in the alimentary canal, or 

 immature encysted in the tissues of their hosts, beyond 

 what may be expected where fishes are exposed to vary- 

 ing sources of infection in the course of their migrations. 



