1919] Rhodes: Binary Fission in Collodictyon triciliatum Carter 243 



comparable to the division of a polar body, but there is no adequate 

 basis for any maturation process. Another phase (pi. 13, tig. 60) 

 was found in which there are two nuclei in a partially constricted 

 individual. This may be a late telophase, but in each nucleus 

 can be seen a small chromatic body near the central karyosome. 

 Furthermore there is a food vacuole containing a recently engulfed 

 Pandorina. This is contrary to the rule. At the beginning of 

 mitosis all food particles are extruded and this is the only instance 

 in which it seems food has been engulfed before karyokinesis is com- 

 pleted. It is interesting, therefore, to contemplate the possibilities. 

 It may be interpreted as follows: 1. A telophase phenomenon, present- 

 ing the anomalies of the small chromatic mass near the karyosome of 

 unknown function, but probably metabolic, and the engulfed Pan- 

 dorina. 2. A somatella of two cells or a suspended telophase which 

 has actively begun to engulf food. 3. Conjugating individuals in 

 which polar bodies are being extruded. Since conjugation has never 

 been observed in living material and this is the only instance capable 

 of such an interpretation, it seems improbable. The first alternative 

 leaves much to be desired, since it gives no explanation of the excep- 

 tional phenomenon. This leaves the interpretation of a suspended 

 telophase or a two-celled somatella as the most probable explanation. 

 It can not be considered of much critical value until further verified 

 and elucidated. We may, however, at least exclude the probability of 

 maturation phenomena. In Collodictyon is found a beautiful illustra- 

 tion of the separation of excessive chromatin from the mass undergoing 

 mitosis, thus freeing that body for its generative function. It presents 

 little probability of sexual phenomena. If I may be allowed to sur- 

 mise, acknowledging how illogical such a surmise is, all such matura- 

 tion phenomena, recorded in the Flagellata, may be nothing more than 

 the amitotic division of the karyosome, as is evident in Collodictyon, 

 a freeing of the nucleus of excessive or surplus chromatin. 



The surface-volume ratio hypothesis is not supported by the cell 

 division of Collodictyon, since all sizes of cells are found undei-going 

 division (pi. 11, figs. 40, 45, pi. 12, figs. 47, 51, 54). There is an 

 apparent indifference to size. 



The theory of nucleao-cytoplasmic ratio is much more difficult to 

 prove or disprove positively. Collodictyon presents a double line of 

 evidence : First, the differential division of the karyosome may be 

 interpreted as either (a) a method of chromatin extrusion, such as has 

 repeatedly been recorded for many, the majority of the Plasmodro- 



