io The Under-Water World 



into being, the entire energy of the 

 protoplasmic cell was concentrated upon 

 battling with the mere physical forces 

 that threatened it from all sides. The 

 protoplasm of the primitive animals 

 enjoyed amazing powers of elasticity, 

 reproduction of lost parts, and im- 

 perviousness to what we understand as 

 pain. The more complex the individual 

 the greater its brain power and the less 

 its ability to regenerate lost parts or 

 reproduce itself by indirect methods. 

 As we shall see, the life force in every 

 animal works steadily and persistently 

 for something better, compelling it to 

 exert its powers to the utmost and to 

 refuse to remain satisfied with that state 

 of life in which it happens to find itself. 

 Whatever the form taken by any 

 individual, one factor has always to 

 be reckoned with change and the 

 creatures that progressed in a world 

 devoid of warm-blooded animals were 



