1919] Rhodes: Binary Fission in Collodictyon tricilUitum CwrU r 213 



in Trichomonas, Costia, and Giardia. Collodictyon must in any case 

 be looked upon as a form of simpler organization and probably of a 

 more primitive type than these parasitic forms. 



The anterior extremity of the sulcus, just beside the base of the 

 flagella. may be modified into a depression (pi. 9, fig. 19) which has 



Fig. C. Escape of Pandorina and subsequent dissolution of Collodictyon due 

 to drying. Diagrammatic. X 750. 1. Pandorina within food vacuole. 2. Pan- 

 dorina swimming away; ruptured surface of Collodictyon. 3, 4. Apparent healing 

 of torn surface. 5. Fusion of ends of protoplasmic processes, enclosing water 

 vacuole; of frequent occurrence. 6-8. Resorption of protoplasmic processes. 

 8, 9. Flattening of body; formation of pathological vacuoles indicative of dis- 

 solution. 10. Bursting of vacuole at anterior region of sulcus. 11. Further dis- 

 solution, rupturing posteriad along the sulcus. 12. Nucleus and blepharoplast 

 freed by dissolution, a. Nucleus; nuclear membrane persisted for two minutes. 

 b. Rupture of nuclear membrane, c. Karvosome; persisted for thirty minutes; 

 finally broke up into small granules, d. Blepharoplast; basal granules sur- 

 rounded by archoplasm, flagella still moving, e. Rupturing of archoplasmic mass; 

 flagella cease beating. 



a probable function of a more specialized cytostome. It takes the form 

 of a permanent depression in an amoeboid surface. It does not usually 

 function in food getting, for this is accomplished by the amoeboid 

 surface of the entire sulcal region. I have, however, observed uni- 

 cellular algae and small dinoflagellates engulfed through or near this 



