72 



MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



telophase stage of division when first found. In a short time the girdle disap- 

 peared, and the cytoplasm divided into two parts (fig. O, 2). In the course of 

 the next two hours a second (fig. 3) and a third (fig. 4) division took place, 

 resulting in the production of eight moieties, each with a single nucleus. Prob- 

 ably owing to adverse conditions under the microscope, the whole cyst began 

 to disintegrate at this stage, without further development. This would appear 

 to be a t}^e of chain- formation not unlike that in falcate cysts of "Pyrocystis," 

 or of thecate forms such as Ccratium (Kofoid, 1909c) and Gonyaulax (Kofoid, 



Fig. O. Multiple fission in Cochlodinium (?) elongatum, sp. nov. 1. First division of nucleus. 2. First 

 division of cytoplasm. 3. Second di^-ision completed. 4. Third division. Further development of these was 

 not followed. X 500. 



1912). It differs strikingly from that in Polykrikos, in which the duplication 

 of external organelles usually precedes nuclear division, whereas here this 

 division was unaccompanied by reduplication of c\i:oplasmic organelles. 



Encystment. — It is evident that encystment plays an unportant part in 

 the life history of these minute organisms. Many forms, especially in the genus 

 Pouclietia, are usually found thus enclosed in the plankton, though generally 

 breaking out of their prison when placed under the stimulation of the high 

 .degree of illumination necessary for the microscope. When first freed from 

 the cyst the flagellate becomes very active, its movements having a much greater 

 rapidity than has been observed in other individuals that have not recently 

 passed through this period of rest. 



