36 MAN, THE ANIMAL 



bound and limited by its organization in man. Our 

 biological unit has to pay some sort of a price be- 

 cause of its association with the higher organiza- 

 tion. This important conclusion stands out in 

 strong contrast in the brief description of free 

 living types of cells that follows. (Fig. 13.) 



The first illustration of a free living biological 

 unit is taken from one of the microscopic animals 

 because we shall find that it helps us to understand 

 many features in man's activities; while our second 

 example is a still smaller unit but clearly a plant 

 whose work is of such great service to mankind 

 that we could not have lived through the centuries 

 without it. 



The ameba (amoeba), figures 13, 14, is one of 



Figure 14. Drawing of an ameba to show how the body is 

 cut into two parts in reproduction. The division begins in 

 the nucleus and later extends to the cytoplasm. W^hen the 

 division is complete two new amebas are found where one 

 was before. 



