178 



OUTLINES OF CLASSIFICATION. 



is what might be expected according to the view that species, like 

 larger groups, have been derived by the modification of pre- 

 existing ancestral forms. 



The foregoing facts do not obviate, but rather emphasize, 

 the necessity of an arrangement of plants and animals in a sys- 

 tem of classification according to relationship. The groups, 

 whether larger or smaller, have a real existence in nature as the 

 expression of resemblances due to community of descent. But 

 it must be clearly understood that they are not isolated and 

 unrelated entities, but simply assemblages of individuals which 

 group themselves naturally about certain centres, but shade off 

 more or less gradually into other groups. 



Outline of the System. As a matter of practical convenience, 

 our primary classification of living things may differ according as 

 the point of view is mainly physiological or morphological. For 

 the sake of convenient reference in the present work, which will 

 consider living things from both points of view, the outlines both 

 of a physiological and a morphological grouping are here given. 



GENERAL CLASSIFICATION ACCORDING TO STRUCTURE. 



LIVING 

 THINGS. 



ONE-CELLED ORGANISMS. 



MANY-CELLED ORGANISMS. 



Protophyta (plants). 

 Protozoa (animals). 



Metaphyta (plants). 

 Metazoa (animals). 



This grouping is extremely convenient, but there is no well- 

 marked limit between one-celled and many-celled organisms, as 

 will appear farther on. Moreover, as has been seen in the fern 

 and earthworm, every many-celled organism during one stage of 

 its existence (germ) is one-celled. 



GENERAL CLASSIFICATION ACCORDING TO FUNCTION. 



LIVING 



THINGS 



(deriving 

 energy from 



the sun). 



GREEN 

 PLANTS. 



COLORLESS 

 PLANTS 



(Fungi, etc.). 



ANIMALS. 



CHARACTERISTICS. 



Able to absorb the kinetic energy of sunlight and 

 to fix it as potential energy in the construction 

 of complex matter, including proteids; therefore, 



Not requiring proteid matter or other energized 

 foods. 



1. Not able to absorb the kinetic energy of sunlight, 



requiring energized foods, but 



2. Not requiring proteid matter. 



1 . Not able to absorb the kinetic energy of sunlight, 



and 



2. Requiring proteid matter as well as other energized 



foods. 



