PROTOZOA 317 



albuminoids. Tnese were very simple at first, and not 

 yet differentiated into cells ; but they had from the 

 beginning the faculty of metabolism. 



Thus the origin of life was determined by the condi- 

 tion of the earth. The living substance is part of the 

 matter of the earth, and has been formed therefrom by 

 spontaneous generation. It was just as necessary an 

 evolution as that of the rocks, when the conditions of it 

 were given. Throughout the whole universe there is 

 an endless chain of causes and effects, and the origin of 

 life comes within this inexorable chain. The further 

 development of the living substance and the moulding 

 of it into the more advanced plants and animals was 

 another necessary consequence of the condition of the 

 earth at the time. These transformations were effects 

 of causes that in turn sprang from other causes. We 

 have long known that all that happens in organic nature 

 is determined by necessary, endless chains of cause 

 and effect. It is the immortal merit of Darwin to 

 have brought life also within this series. 



We may now picture to ourselves the first development 

 of life. We begin with the living substance, the origin 

 of which we have outlined above. In the beginning 

 were the biogens. These must be conceived in the 

 form of living things with a metabolism like that of the 

 actual plant. Their constant break-up would have led 

 to the destruction of all life if they had not had the 

 power of creating their like out of inorganic matter. 

 They cannot, of course, have had any chlorophyll, the 

 green substance that effects the construction of organic 

 matter from inorganic in most of our actual plants. 



