GROWTH AND ORIGIN OF MULTICELLULAR PLANTS. 961 
movement and change of shape, as shown by the protrusion of 
pseudopodia or cilia. That such freedom of movement is due to 
the absence of a resisting external sheath, and not to any innate 
specialty of the di ae of primordial cells as such, is proved by 
the fact that when embrane “ present sufficiently firm be resist 
the outward empties of the protoplasm, but at the e time 
furnished with perforations, — felks plasm rieradel renond® the 
openings in the form of motile threads, as in the Foraminifera and 
tue lar rge e zoospores of Protococcus pecvinlit: and even in the most 
inhi: movements due to the protrusion and retraction of pioute: 
odia i 
8 
situated in the sap-cavity. In primordial cells that do not 5 
any marked fiotiisty, as the oospheres of come vesiculosus, there 
yet evidence of the power of movement change of shape; 
mutual pressure, but on escaping into the water become within a 
very short time perfect spheres; whereas in the genus Sphagnum 
remain in groups until after the development of the epispore, the 
free surface of each fa eee warted, whereas the portions that 
were in contact remain 
Alge are roluded those forms of life which manifest the 
t of ce , as also the earliest 
ae 
or 
By 
~O 
SE 
oO 
a) 
"8. 
5 
oO 
m 
B 
8 
2 
4 
= 
ef. 
5 
© 
known to biologists. Sachs* alludes to its presence as follows :— 
“ The internal Sg = protoplasm usually manifests te 
layer surrounding the irc all with which i remains i the 
most intimate contact. ees portion of a protoplasm- —_ = 
mediately surrounds itself, when it becomes isolated, with su 
skin.” In Alow the cell-wall appears in the middle of this aki, oa 
inner portion "bein ing known as the cytio — ; the 
external part forms the sheath, which in oe instances is add 
to by subsequent secretion from the protoplasm 
ring the vegetative period protoplasm ids to its bulk by the 
assimilation of beschinets matter, and in primitive types, where life 
manifests but little “idividuality, extends along the lines of least 
resistance, or passively obeys the directive indeed of the more 
potent surplus of chemical and Sag forces, which are antago- 
a 
ifesting 
toplasm ; hence in the = whic m both vege- 
tative and reprodustive standpoint may be sstantr Tet as including 
* «Text-book of Botany,’ 2nd English ed, p. 38. 
