172 ANIMALS AND PLANTS. [LECT. 



guishable by any important character from our Hetero- 

 mita, and extraordinarily like it in some respects. 

 And yet this " Monad " can be traced, step by step, 

 through the series of metamorphoses which I have 

 described, until it assumes the features of an organism, 

 which is as much a plant as is an oak or an elm. 



Moreover, it would be possible to pursue the 

 analogy farther. Under certain circumstances, a pro- 

 cess of conjugation takes place in the Peronospora. 

 Two separate portions of its protoplasm become fused 

 together, surround themselves with a thick coat, and 

 give rise to a sort of vegetable egg called an oospore. 

 After a period of rest, the contents of the oospore 

 break up into a number of zoospores like those 

 already described, each of which, after a period of 

 activity, germinates in the ordinary way. This process 

 obviously corresponds with the conjugation and sub- 

 sequent 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, without 

 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 



