170 THE SCIENCE OF LIFE. 



CHAPTER XII. 



RADIATA. 



If we are astonished that so great deeds should proceed from the little 

 and low, it is because we fail to appreciate that little things, even the least 

 of living or physical existences in nature, are, under God, expressions 

 throughout of comprehensive laws, laws that govern alike the small and 

 the great. DANA, Corals and Coral Makers. 



1. IN the simple Protophytes and Protozoa we find the 

 essential structure to be a single cell, or mass, of bio- 

 plasm, having in one vegetable and in the other animal 

 characteristics. In some instances there is a colony, or 

 association, of bioplasts, with certain mutual relations ; 

 but as each bioplast is but loosely connected with the 

 others, and is capable of living and performing all its 

 functions while in a state of independence, these colo- 

 nies are conveniently considered among primordial types. 

 In the higher forms of life, either animal or vegetable, 

 each individual is composed of many bioplasts, derived 

 by subdivision of the primitive mass. With the division 

 of the structure there is also a differentiation of function, 

 so that no bioplasts of the structure, save those which 

 are appropriated to reproduction, can normally pursue 

 an independent existence. 



2. The Radiate type of animal life is characterized by 

 the idea expressed in the word radiation. " In Radiates 

 we have no prominent bilateral symmetry, such as ex- 

 ists in all other animals, but an all-sided symmetry, in 



