188 ANIMALS AND PLANTS vi 



ordinary way. This process obviously corresponds 

 with the conjugation and subsequent setting free 

 of germs in the Heteromita. 



But it may be said that the Peronospora is, 

 after all, a questionable sort of plant ; that it seems 

 to be wanting in the manufacturing power, selected 

 as the main distinctive character of vegetable 

 life; or, at any rate, that there is no proof that 

 it does not get its protein matter ready made 

 from the potato plant. 



Let us, therefore, take a case which is not open 

 to these objections. 



There are some small plants known to botanists 

 as members of the genus Coleochcete, which, with- 

 out being truly parasitic, grow upon certain 

 water-weeds, as lichens grow upon trees. The 

 little plant has the form of an elegant green star, 

 the branching arms of which are divided into 

 cells. Its greenness is due to its chlorophyll, and 

 it undoubtedly has the manufacturing power in 

 full degree, decomposing carbonic acid and setting 

 oxygen free, under the influence of sunlight. But 

 the protoplasmic contents of some of the cells of 

 which the plant is made up occasionally divide, by 

 a method similar to that which effects the division 

 of the contents of the Peronospora spore ; and the 

 severed portions are then set free as active monad- 

 like zoospores. Each is oval and is provided at 

 one extremity with two long active cilia. Pro- 

 pelled by these, it swims about for a longer or 



