HAECKEL AND PFLUGER 79 



not present now, and that, though it may at first glance seem 

 paradoxical, was the absence of life. Only in the absence 

 of organisms could life develop. Organic substances arising 

 on the surface of the Earth at present w^ould not be able to 

 undergo prolonged evolution. After a comparatively short 

 time they would be annihilated, devoured by the multitude 

 of organisms, well equipped for the struggle for existence, 

 which inhabit all parts of the earth, w^ater and air. On the 

 other hand, in the remote past when our planet was still 

 sterile, the process of evolution of organic substances could 

 be prolonged indefinitely and this could have led up to the 

 emergence of the primaeval living things in accordance with 

 certain natural laws which we shall discuss later. 



This idea, as we now know, was already clear to Darwin, 

 who -^vrote in a letter dated 1871 as follows: 



It is often said that all the conditions for the first production 

 of a living organism are present, which could ever have been 

 present. But if (and oh! what a big if!) we could conceive in 

 some warm little pond, with all sorts of ammonia and phosphoric 

 salts, light, heat, electricity, etc., present, that a protein com- 

 pound was chemically formed ready to undergo still more com- 

 plex changes, at the present day such matter would be instantly 

 devoured or absorbed, which would not have been the case 

 before living creatures were formed. ^^ 



Nevertheless, at the end of last century and the begin- 

 ning of the present one, the mechanistic concept of the self- 

 formation of life under the influence of some elementary 

 physical forces and effects still prevailed extensively in the 

 minds of scientists. Many of them were so carried away 

 as to make assumptions concerning the nature of these forces 

 and to draw a picture of the emergence of living things from 

 inorganic matter under the circumstances obtaining on the 

 primaeval Earth. Among these forces were included elec- 

 trical discharges, ultraviolet radiations, the forces of chemical 

 affinity and later even the radioactivity of the elements. As 

 we shall see later, all these factors must certainly have played 

 an important part as sources of energy in the transformation 

 of organic substances in the process of their evolution on 

 the primaeval Earth. However, in themselves they certainly 



