CHLOROPHYCE.E 181 



However Cienkowski, one of the first to observe 

 these " yellow cells " and to indicate their algal 

 character, long ago based his argument on the 

 observation that they continued to live and multiply 

 long after the death of the animal ; and Geddes, as 

 well as Brandt, fully established their algal character 

 by a series of minute observations made simul- 

 taneously and independently. 



Reproduction is, as has been said, by the separation 

 of vegetative cells. 



The Geographical Distribution of the order is world- 

 wide. Zoochlorella has a wide distribution in the 

 warmer seas, while Prasiola occurs in fresh-waters, 

 as well as in the sea, throughout the world. Palmo- 

 phyllum is confined to Europe. Prasiola is the only 

 genus recorded in British seas, though the order is 

 represented by many genera in the fresh-waters of 

 this country. 



PERIDINIE^E. 



General Characters. Judged by our present know- 

 ledge of this order, it occupies a position on the 

 borderland between the plant and animal king- 

 doms, while the balance of evidence certainly leans 

 towards our regarding them as plants. Some of the 

 forms, like Ccratium, are certainly plants. They 

 occur in very varied forms, always free and never 

 attached, except to each other in chains, as in Cera- 

 tium Tripos, both in fresh-waters and the sea, and 

 have, some of them, membranes, others not. They 

 pass through a ciliated motile phase and a resting 



