vi ANIJVfALS AND PLANTS 189 



shorter time, but at length comes to a state of 

 rest and gradually grows into a Coleochcete. 

 Moreover, as in the Peronospora, conjugation may 

 take place and result in an oospore ; the contents 

 of which divide and are set free as monadiform 

 germs. 



If the whole history of the zoospores of Perono- 

 spora and of Goleockcete were unknown, they would 

 undoubtedly be classed among " Monads " with 

 the same right as Heteromita ; why then may not 

 Heteromita be a plant, even though the cycle of 

 forms through which it passes shows no terms 

 quite so complex as those which occur in Perono- 

 spora and Cohochcete? And, in fact, there are 

 some green organisms, in every respect charac- 

 teristically plants, such as Chlamydomonas, 

 and the common Volvox, or so-called " Globe 

 animalcule," which run through a cycle of forms 

 of just the same simple character as those of 

 Heteromita. 



The name of Chlamydomonas is applied to certain 

 microscopic green bodies, each of which consists of 

 a protoplasmic central substance invested by a 

 structureless sac. The latter contains cellulose, as 

 in ordinary plants; and the chlorophyll which 

 gives the green colour enables the Chlamydomonas 

 to decompose carbonic acid and fix carbon as they 

 do. Two long cilia protrude through the cell-wall, 

 and effect the rapid locomotion of this " monad," 

 which, in all respects except its mobility, is 



