226 ANIMAL BIOLOGY 



abstracting oxygen from its compounds with carbon, hydrogen, 

 sulfur, and other elements and delivering it to the atmosphere. 

 Not much energy would be absorbed by a transparent liquid; 

 but such reactions would occur particularly in water containing 

 compounds of iron in solution or suspension since these compounds 

 would absorb the solar energy. In this way compounds of nitro- 

 gen, carbon, etc., accumulated in the water or damp earth; and 

 further reactions, anabolic and katabolic, occurred among them 

 by virtue of the lability of the nitrogen compounds. Life at this 

 stage was of the humblest kind since there were no definite organ- 

 isms, only diffuse substances trading in energy, and between this 

 stage and the evolution of cellular organisms an immense period 

 elapsed. 



5. Troland's Theory 



With the increasing realization of the importance of enzymes in 

 the economy of organisms, it is not strange that in these chemical 

 bodies has been sought the key to life's origin, and accordingly we 

 find Troland stating that life is something which has been built up 

 about the enzyme. This author assumes that, at some moment in 

 Earth history, a small amount of a certain autocatalytic enzyme 

 suddenly appeared at a definite point within the yet warm ocean 

 waters which contained in solution various substances reacting very 

 slowly to produce an oily liquid which did not mix with water. If, 

 when this occurred, the enzyme became related to the reaction in 

 such a way as to greatly increase its rate, Troland believes it is ob- 

 vious that the enzyme would become enveloped in the oily material 

 resulting from the reaction, and the little oil drop would increase 

 until it was split into smaller globules, provided the original sub- 

 stances which combined were soluble in oil as well as in water. Thus 

 arose, according to Troland, the first and simplest life-substance, 

 possessing the power of indefinitely continued growth. 



6. Osborns Theory 



Starting with the assumption that the primal earth, air, and 

 water contained all the chemical elements and three of the more 

 simple but important chemical compounds — water, nitrates, 

 and carbon dioxide, Osborn suggests that an initial step in the 

 origin of life was the bringing of these elements into combined ac- 

 tion. This took place when the Earth's surface and waters had 



