Linton. — Trematode Parasites of Fish 257 



In collecting these trematodes from the loon, a portion 

 of the intestine was scraped, the scrapings washed and the 

 water decanted. The worms, then seen for the first time, 

 were collected from the bottom of the dish. As their 

 presence was not suspected until the material had been 

 washed, no effort was made to remove all the worms that 

 might be lodged in the mucous membrane of the intestine. 

 Notwithstanding this, 4,789 specimens were counted. They 

 presented a great variety of contraction shapes, but at rest 

 they were usually long oval, widest at about the level of the 

 posterior edge of the genital sucker, or a little back of 

 that point, tapering most toward the anterior end. Some 

 were nearly linear from the genital sucker to the anterior 

 end, with the posterior portion broadly rounded; others 

 were nearly linear throughout. There is considerable varia- 

 tion in size, though all are small, being less than 1 milli- 

 meter in length when uncompressed. One measured 0.75 

 millimeter in length, and 0.35 millimeter in greatest breadth ; 

 ova 0.04 by 0.02 millimeter. Further details will be given 

 in a special report. 



ECONOMIC CONSIDERATIONS 



Since the thought of the presence of parasitic worms in 

 our foodstuffs is such a disquieting one, this paper should 

 not be brought to a close without at least a brief considera- 

 tion of the insistent inquiry respecting the harmfulness to 

 man of these parasites and of the question of their control, 

 or extermination. 



So far as known there is no danger that any of the 

 parasites considered in this paper will develop in man. 

 When it is remembered that the infected fish are eaten by a 

 large number of other fish, in which these parasites do not 

 come to maturity, and that even among the fish-eating 

 birds the adult of the flesh parasite has been found in only 

 two species, the bittern and the heron, and that the adult of 

 the skin parasite has been recognized in but one species, the 



