1885.] Comparative Physiology and Psychology. 7 
forces influence food procuring. Atavism is prominent in doing 
that which drives from a base of supplies or want of foresight in 
improvidence. 
Prehension is an accessory to locomotion, and both are assimi- 
lative acts, or acts which have for their end the assimilative. 
This also is evident in full development, for every act or move- 
ment of the body is of a prehensile nature. Leg movements take 
hold of the ground through gravitation to carry the body in search 
of food; hands and arms being directly prehensile; jaws are pre- 
hensile in their food grasp; ribs are prehensile in their assisting 
oxygen introduction, that gas being a food. In snakes the ribs 
are locomotory prehensile. 
We thus have.all the physical forces, including gravitation and 
chemical energy, acting upon the low organism to cause al its 
motions. Just as the heat of the sun overcomes by its gravity 
the earth’s, and lifts billions of tons of water from the ocean to 
allow it to fall again in obedience to terrestrial attractive force, so 
may the “vitality” of an animal or plant, apparently working 
against physical laws, lift the child from the embryo, the tree 
from the seed, but eventually the cycle is complete and the prim- 
itive elements are separated in “death” to reenter at once upon 
other changes. The natural forces are masked in life-phenomena 
as the law of gravitation is, though the direct agent, not recog- 
nized in the upward rush of the fountain. 
The Ameeba assimilates organic matter and breathes as it uses 
up oxygen and exhales carbonic acid. To complete the objective 
study of the Amceba we observe that it grows as a consequence 
of its eating, and that owing to its growth and the operation of 
the attraction of gravitation, a force too often neglected in con- 
sideration by physiologists, fission or reproduction occurs, as the 
cohesive attraction of its molecules cannot pass beyond a certain 
limit, and the extra weight is gravitated, excreted off, a process 
still evident in all animal reproduction and through excretory 
channels also. 
We also see that the po act is identical with eating in the 
so-called neutral, genuine hermaphrodite, form. This is more 
apparent in other Protozoa as a differentiation. I append my 
article on this subject from Science (N. Y.), June 1, 1881: 
A paper on Researches into the Life-history of the Monads, by W. H. Dallinger, 
F.R.M.S., and J. Drysdale, M.D., was read before the Royal Microscopical Society, 
