Moore. — Neiv Species of Parasite in Trout. 89 



lucida from permanent preparations, under oil immersion 1.5, ocular 10-X. 



Smears were made of the intestinal contents and treated by the wet Schau- 



dinn method or in Zenker's fluid. Stain : iron-haematoxylin, or Delafield 



and eosin following Zenker's fixative. 



Abbreviations: nuc, nucleus; fl. 1, first flagellum; fl. 2, second flagellun. , 

 fl. 3, third flagellum ; fl. 4, posterior flagellum ; ax., axo- 

 siyles ; gr., groove ; cyt., disk or cytostome ; pb., parabasal 

 bodies. 



Plate I. — Octomitus salmonis. 



1. Typical adult, motile, individual showing six anterior and two posteriot 



flagella, nuclei, and axostyles. Found chiefly in the fore-intestine 

 when infection is most severe. 



2. A stage in the longitudinal division of the adult form. This stage 



and the preliminary ones leading to it were frequently observed 

 on smears of fresh material, and represent a common mode of mul- 

 tiplication. 



3. A newly encysted adult Octomitus. 



4. A stage in encystment later than in 3. 



5. A cyst at stage later than that in 4, showing multiplication of nuclei — 



perhaps a phase in the sexual cycle. 



6. Advanced stage of that shown in 5, showing formation of what are 



perhaps the eggs. 



7. An encysted form which has developed within the epithelical cells of 



the intestine — perhaps a "Hexamitiis stage." 



8. Young Octomitus. E^rly stage showing single flagellum and attach- 



ment disk at bottom. 

 '9. Longitudinal division of young form, a method of rapid increase of 

 individuals. Attachment disk shown at right of upper individual. 



10. Side view of young form, a slightly older than that in 8, showing strong 



resemblance to young Giardia. Attachment disk at bottom. 



11. Further advancement of young form, showing two flagella. 



12. Advanced young form with three flagella. The attachment disk has 



disappeared and the prolongation at the bottom suggests the future 

 trailing flagella. 



Plate II — Hexamitidae. 



13. Hexamitus itttestinalis Duj. Specimen from intestine of a frog. 



14. Octomitus intestinalis truttae Schmidt. After Schmidt, W., 1920. 



15. Giardia cnterica Grassi. Human parasite. After Kofoid, C. A. and 



Swezy, O., 1922. 



16. Octomitus salmonis. Forms encysted in tips of epithelial cells sloughed 



off intestinal tract, a, single individual; b, division of individual in 

 the encysted stage. 



APPENDIX. 



The data in the tables of Dissolved Oxygen Determinations 

 and Chemical Analysis are appended by courtesy of the Commis- 



