Moore. — New Species of Parasite in Trout. 79 



readily explained by the neighborly way we have of exchanging 

 eggs and fish, by keeping adult brood fish which are carriers, 

 and by permitting infected fish in the source of the hatchery 

 water supply. 



It has been thought that a probable source of the organism, 

 Octomitus, in the hatchery might be derived from the frog which 

 harbors a somewhat similar intestinal parasite. Hexamitus in- 

 testinalis Dujardin (13) and comparative studies on local ma- 

 terial were made to elucidate this point. Two species of froga, 

 the pickerel- frog (Rana palustric Le Conte) and the green- frog 

 (Rana clamitans Latreille) common in the locality of Bath, N. Y., 

 where the epidemic of octomitiasis occurred, were found to be 

 heavily parasitized with Hexamitus. The frogs had access to the 

 water supply of the hatchery and must have naturally spread 

 infection in it. However, a careful search through many pre- 

 pared slides of material from parasitized frogs and fish has given 

 what seems to be convincing proof that the parasite, Hexamitus 

 mtestinalis Dujardin, of the frog and Octomitus salmonis of the 

 trout are specific for their hosts. 



OCTOMITUS SALMONIS MOORE. 



Octomitus salmonis Moore is a binucleate, bilateral, parasitic, 

 octo-flagellate belonging to the family Hexamitidae of the order 

 Polymastigina. It is an intestinal parasite causing the disease 

 Octomitiasis in various species of trout. The actively swim- 

 ming adult form, or trophozoite (1) is pear-shaped in outline, 

 broad at the anterior end and bluntly pointed at the tail. The 

 body in action is exceedingly mobile, but the pyriform outline 

 is generally characteristic. In size the flagellate is minute, vary- 

 ing in length from 6 to 12 micra and in width from 3.5 to 5 micra. 



The two nuclei (nuc.) are conspicuous at the anterior end. 

 From their changing position, when the organism is moving, the 

 nuclei appear to be connected with the blepharoplast complex, 

 the mass of deeply staining granules in front of the nuclei, from 

 which arise the three pairs of anterior flagella (fl. 1, 2 and 3). 

 This complex consists of two sets of granules bilaterally ar- 

 ranged. In each set there is a forward granule, which lies at the 

 base of a single flagellum (fl. 1) and two immediately behind, ap- 

 parently fused, giving rise to the next two pairs of flagella (fl. 

 2 and 3). The pair of axostyles (ax.) extends backward from 



