PROTOPLASM AND ITS PROPERTIES. 129 
(1) Absorption. 
(2) Metabolism. 
(3) Excretion. 
(4) Reproduction and growth. 
(5) Automatic powers.’ 
(6) Contractility. 
(7) Irritability. 
(1), (2), and (3) are not so readily studied in 
the slime-moulds as in some other plants, but 
unless one can believe in the manufacture of 
something out of nothing, he must conclude 
that these simple plants make their growth 
at the expense of materials drawn from the 
water and the decaying matter on which they 
are found.’ 
‘Another important characteristic of living 
protoplasm, which the student may establish 
by his own experiments, is: the power of 
resisting some chemical and physical changes. 
Living cells and their contents are not always 
affected by acids, alkalies, staining solutions, 
heat or cold as the same material would be 
affected after it is dead or before it becomes 
alive. 
-163. Circulation of Protoplasm. — When 
confined by a cell wall, protoplasm often mani- 
fests a beautiful and constant rotating move- 
ment, traveling incessantly up one side of the 
Fig. 103.—Sting. 
ing Hair of Net- 
tle, with Nucleus. 
The arrows show 
the direction of 
the currents in 
the protoplasm. 
* 1That is, the power of originating movements not wholly and directly caused by 
any external impulse, for instance, the lashing motion of the cilia of the swarm- 
spores of slime-moulds or the slow periodic movements of some leaves, even when 
exposed to an unchanging temperature and amount of light. 
' 2Tt would of course be well for the pupil to make careful studies of Ama@ba and 
of one or more of the ciliated animaleules. If time will admit of this, the teacher 
may consult Huxley and Martin’s Elementary Biology, under Ameba and Vorticella. 
