34 EVOLUTION OF PLANTS 



tinues for a longer or shorter time, and may multiply 

 by fission and thus produce a large number of indi- 

 viduals which finally lose the single cilium or flagellum, 

 and creep about like amoebae (E). Finally, as in the 

 higher Monera, these individuals fuse into a single large 

 mass or plasmodium. 



A study of these two groups, Monera and Myceto- 

 zoa, illustrates in a very instructive way how a consid- 

 erable degree of differentiation is possible within the 

 limits of a group whose structure is of the simplest 

 character. The two classes are probably offshoots of 

 a common stock very near the bottom of the scale of 

 living organisms. It is not likely that either class has 

 much in common with the higher plants or animals, 

 but the constant occurrence in both of flagellate swarm - 

 spores indicates that the latter may, perhaps, represent 

 the simplest expression of living things known to us, 

 and that from some such forms have sprung not only 

 the Monera and Mycetozoa, but also the higher animals 

 and plants. 



SCHIZOPHYTA (Fission Plants) 



Under this name are now united a large number of 

 plants of very simple organization, of which the most 

 familiar are the Bacteria. Owing to the extreme 

 minuteness of many of them, it is not possible to deter- 

 mine positively how far their apparently excessive 

 simplicity is real. With better methods of fixing and 

 staining, and improved microscopic lenses, the bacteria 

 are revealing structures which formerly escaped detec- 

 tion, and it is reasonable to suppose that there is still 

 much to be learned as to their minute structure. 



