18 ANIMAL FORMS 
The loss in bodily waste is continually made good by 
the manufacture of the food into protoplasm, and if the in- 
come be greater than the outgo growth ensues. But, as in 
all other forms, growth is limited, and ultimately the cell is 
destined to divide, resulting in two new individuals. This 
process may be repeated many times, but not indefinitely, 
for sooner or later various members of the same species 
unite in pairs temporarily or permanently, exchange nu- 
clear material, and separate again with apparently renewed 
energy and the ability to divide for many generations. 
21. Simple and complex animals.—It is important to note 
that these same processes of waste, repair, growth, feeling, 
motion, and multiplication are the same as those of the 
squirrel, and, furthermore, are common to all living crea- 
tures, so that the difference between animals is not in their 
activities, but in their bodily mechanisms ; and according to 
the perfection of this, the animal is high or low in the 
scale: Comparing, for example, the Ameda and Slipper 
Animalcule, which are relatively low and high Protozoa, we 
find in the former that any part of the body serves in loco- 
motion and in the capture of food, while in the latter these 
same functions are performed by definite structures, the 
cilia and gullet. Now it is well known that a workman is 
able to make better watch-springs, when this is his sole 
duty, than another who must make all parts of the watch; 
and likewise where a definite task is performed by a defi- 
nite structure, it is more efficiently done than where any 
and every part of the body must carry it on. So the 
Ameba, in which definite tasks are performed by any part 
of the body indifferently, is less perfect and thus lower than 
the Parameciwm, where these functions are performed by 
special organs. As we ascend the scale of life we find this 
division of labor among special parts of the body more 
complete, the organs and therefore the animal more com- 
plex, and better fitted to carry on the work of its life. 
