80 American Fisheries Society. 



tract, though they are generally most numerous near the seat 

 of infection in the fore-intestinal region. While the adults 

 are thus swimming about ti'ansformations take place in the 

 various ways illustrated in the diagram, with the resultant 

 production of structures concerned in the further spread of 

 infection. Multiplication (B) occurs by binary fission, the 

 division of one individual into two, and by another more pro- 

 lific means, schizogony, the intervening structure in this case 

 being a spore or cyst of temporary nature which functions ap- 

 parently in the spread of local infection. 



The development of another type of spore, also a multinu- 

 cleated structure (E), appears to follow binary fission. Such 

 a spore possesses a hard resistant wall, passes to the exterior 

 in the feces and functions in the transmission of the parasite 

 from fish to fish. It is the structure which doubtless accounts 

 for the presence of juveniles in the stomach in the initiation 

 of new infection. 



THE LIFE CYCLE. 



By assembling the important stages in the life history of 

 Octomitus in their natural sequence of development (Fig. 2), 

 it is possible to show more directly how the organism is 

 equipped for self perpetuation. Starting the cycle with an in- 

 fected epithelial cell (1), encystment stages carry forward the 

 development from minute juvenile stages to the adult stage 

 (II), by a route in all probability involving schizogony and 

 supplemented by steps shown in the side chain I, Ii, I2-II). 



Dr. Davis* has made a distinct contribution to our under- 

 standing of the life history of Octomitus by pointing out in- 

 tracellular development and indicating methods of increase of 

 the organism in the intracellular stages. These findings are 

 corroborated by the writer's studies, though exception is taken 

 to the interpretation of structural features concerned in cer- 

 tain of the developmental stages. For example. Dr. Davis pos- 

 tulates a development of transitional stages whereby binu- 

 cleated individuals (adults) arise from uninucleated structures 

 (juveniles). The writer's study of culture material in which 

 exceedingly minute juveniles have been observed indicate that 

 the organism throughout its life history is binucleated. 



Passing from the adult (II), which is the final product 

 of encystment, two lines of development seem indicated within 

 the intestinal tract, one involving the series of steps included 

 in II-V, suggesting possibilities of increase by schizogony 

 from a temporary spore (III), and the other proceeding from 

 the division of an adult by binary fission (VI) eventuating in 



*Davis, H. S. Observations on an intestinal flagellate of trout. Journ. of 

 Parasitology, 9: 153-160, 1923. 



