Moore. — New Species of Parasite in Trout. 81 



motile, juvenile phase, in which growth and rapid multiplication 

 by binary fission take place. By inoculating a highly alkaline 

 and dilute fish broth with the adult organism, the growth stages 

 shown in (8-12) were obtained. It is assumed that the adult 

 passed quickly into a cyst, possibly a multiplication cyst, and 

 this gave rise to numerous minute structures, resembling masses 

 of deeply staining, coccus-like bodies that soon developed into 

 the recognizable form of (8). The presence of a cytostome or 

 "mouth" is apparent in the young (10), but it is a feature which 

 is unrecognizable, if not lost altogether, in the adult stage. The 

 last step which appears to be possible under conditions of arti- 

 ficial culture is shown by (12). Without doubt further trans- 

 formation necessitates encystment within the intestinal and 

 caecal wall, as suggested by the recent unpublished researches 

 of Dr. H. S. Davis, * who simultaneously studied Octomitus dur- 

 ing the past summer. His observations indicate that develop- 

 mental stages also occur within the epithelial cells of the in- 

 testinal caeca and of the intestine. Such development apparently 

 carries the organism through to the adult stage (7). It is possi- 

 ble that the young flagellates, motile and very mobile, slip into 

 the soft epithelial tissue and there undergo final transformation. 



Octomitus Salmonis a New Species. The organism in ques- 

 tion is characterized by a binucleate, single celled structure with 

 eight flagella. On the basis of these characters it obviously be- 

 longs to the family Hexamitidae, which includes such related 

 genera as Hexamitus (13), Octomitus (14) and Giardia (15). 



In determining the generic position of the new organism the 

 criteria of classification are on the whole less easily applicable. 

 The presence of a disk or cytostome is a structural feature to be 

 reckoned with. It is conspicuous in Giardia and sharply sets it 

 off from the other genera pictured. Schmidt (1920) argues that 

 a cytostome is suggested for Octomitus by the behavior of the 

 organism he described. His figures indicate a somewhat con- 

 tracted structure of this kind. In the culture forms of the new 

 organism (8-12) a cytostome is present, in the juveniles, but it 

 is not apparent in the adults, although their behavior in this 

 stage agrees with Schmidt's description of Octomitus. In Hex- 

 amitus no evidence of a cytostome has been adduced. By com- 



* Loc. cit. 



