20 MAN, — THE ANIMAL 



a variety of mutilations and still retain its life, thus 

 constantly having a changing normal, due to the 

 influence of its living condition. 



4. The Law Governing the Size of Living 

 Bodies. — -The size and shape of living bodies can- 

 not be stated in any general expression. Some are 

 so small that the highest power of the microscope 

 has failed to reveal them, while the giant redwood 

 trees tower above all other living things by many 

 feet (Fig. i). Between these two extremes are 

 found a multitude of sizes each of which is charac- 

 teristic of a given species. Animals have never 

 grown to such large size as some of the trees, 

 although some of the fossil forms were nearly one 

 hundred feet long (Fig. 2). When a given kind 

 of plant or animal comes to have a certain size and 

 shape, there are only minor variations from year 

 to year, as both appear to have become fixed for 

 a given species and are continued from generation 

 to generation by heredity. The law regulating the 

 size of living things is most variable and yet defi- 

 nite limits are known to exist. These limits are 

 intimately related to the conditions set forth in 

 the 9th law. 



5. The Law Governing the Age of Living 

 Bodies. — A number of the unicellular organisms 

 retain their individuality for not more than thirty 

 minutes under normal feeding conditions (Fig. 3) ; 

 while the great redwood trees have retained their 



