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 ameebe (EZ). 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. 
