Properties and Activities of Living Protoplasm 99 



In lower types of organisms a part of an organism may have the 

 abiUty of restoring all the missing parts for an entirely new individual. 

 For instance, one ray or arm of a starfish may be removed (Fig. 28). 

 The missing ray will be replaced, and the removed ray has the ability 

 to add the four rays to itself in order to make two complete individuals, 

 each with the normal number of five rays. The flatworm (Planaria) 

 may be cut into several transverse pieces. Each resulting piece has the 

 inherent ability to regenerate some form of Planaria (Fig. 28). The 

 earthworm may regenerate a missing "head" or "tail" region. The 

 Hydra may replace missing tentacles, layers of cells, or even the mouth 

 region (Fig. 28) . 



IX. LIVING AND NONLIVING THINGS CONTRASTED 



A survey of various living organisms as a group contrasted with dif- 

 ferent kinds of nonliving substances reveals certain differences. Many 

 of these dififerences are quite apparent upon casual observation, and 

 additional ones will be observed when more detailed studies are made. 

 Most biologists agree that the phenomena of living organisms are more 

 complex than comparable phenomena in nonliving substances but that 

 both are more or less associated with chemical and physical processes. The 

 mechanistic theory suggests that all vital phenomena are to be explained 

 by a complete understanding of all the chemical and physical forces 

 which operate in living protoplasm — that life is merely the result of the 

 proper interactions and counteractions of these forces. The vitalistic 

 theory suggests that some unique, supernatural force or power which is 

 not reducible to the terms of physics and chemistry is responsible for 

 the initiation, continuity, and control of vital activities — that this "extra 

 something" differentiates living from nonliving and that science shall 

 never be able to create life or be able to understand it completely. The 

 more significant characteristics of living organisms and nonliving sub- 

 stances are contrasted briefly in the accompanying table. 



LIVING (ANIMATE) ORGANISMS 



NONLIVING (INANIMATE) 

 SUBSTANCES 



COMPOSITION 



A,ll living organisms, both plant and 

 animal, have been found to be com- 

 posed of a highly organized, chemi- 

 cally complex protoplasm with its 

 unique characteristic chemical and 

 physical properties. 



Even though certain nonliving sub- 

 stances may have a definite chemical 

 composition and specific physical 

 properties, none of them have ever 

 been observ^ed to be composed of 

 protoplasm. 



