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 Amceba 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 

 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 

 Amceba, in which definite tasks are performed by any part 

 of the body indifferently, is less perfect and thus lower than 

 the Paramcecium, 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. 



