1919] Rhodes : Binary Fission m Collodictyon triciliatum Carter 215 



the body. Even then the nucleus persisted as a unit for some two 

 minutes, when the nuclear membrane ruptured and the karyosome 

 alone remained as a unit, retaining its form for over half an hour. 

 The blepharoplast persisted as an irregular granular mass surround- 

 ing the two basal granules. As long as this mass remained as a unit, 

 the flagella could be seen to wave back and forth, but ceased moving 

 as soon as the mass disintegrated. 



It is especially noticeable that the body may be distended, elon- 

 gated, or distorted by newly engulfed food (pi. 9, figs. 19-27). It may 

 elongate to twice its normal length by inclusions of filamentous algae, 

 desmids, or diatoms. Such elongation is usually, though not always, 

 anteroposteriorly. The modifications due to inclusions of such organ- 

 isms as Scenedesmus or Lagerheimia I have already mentioned. 

 Chlorella and Protococcus when engulfed were arranged peripherally 

 within the vacuolated cytoplasm, just underneath the surface reticu- 

 lum. At times this made the animal appear perfectly green. These 

 frequently popped out through the pellicle and when first observed 

 made me think of zooids from flagellated forms in multiple fission. 

 Such a condition was but temporary, however, the algae either being 

 digested for food, early showing the surrounding vacuole, or else, I am 

 led to believe, at times assuming the state of transient symbiosis. For 

 three months such a congested condition was both typical and domi- 

 nant. Seldom was Chlorella digested and I am inclined strongly to 

 the idea of transient, or facultative symbiosis. 



As seen in the living state, the cytoplasm consists of large, hyaline 

 vacuoles, in the interstices of which are smaller vacuoles, and the spaces 

 between these filled with granules or plasmosomes in a fluid matrix 

 (pi. 8, fig. 5). The periphery of each vacuole seems to consist of a 

 definite membrane, more the result of a turgid surface tension, while 

 the interior is filled with a hyaline fluid. 



The surface of the cytoplasm consists of smaller vacuoles with a 

 greater number of granules. The arrangement of these gives the 

 appearance of a surface reticulum, with the larger, deeper vacuoles 

 lying against or within it. "When disintegration takes place, the 

 pellicle ruptures, the cytoplasm goes to pieces rapidly, the hyaline fluid 

 diffusing into the water, and the granules, which do not appear nearly 

 so numerous as the mass of the organism might indicate, are scattered 

 by diffusion currents. 



The nucleus possesses no vacuoles, but seems to consist, much as the 

 blepharoplast and the immediately surrounding cytoplasm, of granules 



