430 EVOLUTION AND GENETICS 



The Factors in the Existence of Living Organisms. This 

 unprejudiced analysis demands first of all an understanding of 

 organic existence. What lies behind the living organism? Why 

 are organisms definitely of this or that species, and why do they 

 live? We need not carry this inquiry as far as the origin of life, 

 for a significant answer is found in the components of existence 

 mentioned from time to time in previous chapters. The organism 

 has definite qualities because they are its heritage. They are not 

 absolutely fixed, for variation is universal, but within the limits 

 of variation they are the same throughout a given species. The 

 organism depends for the expression of these qualities upon things 

 secured from without — from its environment. Its life depends 

 upon its inherent power to secure and use these things. Response 

 to the environment, in brief, is a third factor arising from the other 

 two, and organic existence depends upon the interaction of these 

 three. Without any one of them life must cease. Modification 

 of any one beyond its normal range can only result in abnormal 

 existence or death. 



Such an analysis does not explain ultimate causes, nor does it 

 pretend to do so, but in the realization that the three factors 

 are indispensable is disclosed the fallacy of many theories of 

 evolution. We are at present unable to do more than speculate 

 on ultimate causes. Whether life is due to the existence in the 

 organism of some cosmic influence other than those whose existence 

 is proved, or whether it is merely an intricate expression of familiar 

 matter and energy operating in space and time, we do not know. 

 The fact remains, however, that living things are governed by 

 natural laws, whatever may be the activating principle, and it 

 is the immediate task of evolutionists to explain acceptably how 

 organisms are shaped, how species are formed, on the basis of 

 known l)iological facts. 



The heritage has often appealed to biologists as a thing 

 apart, which expresses itself in a definite way in spite of outer 

 influences. It does attain remarkably vmiform results in the many 

 individuals composing a species, but we may well ask whether 

 these results are ever, after all, an outcome of the heritage alone. 

 The heritage is sufficiently definite and potent that no one would 

 plant an acorn to raise a peach tree or buy wolves to stock a dairy 

 farm. The egg of a hen can produce nothing Imt a chick. Keep 

 it in a cool place and it remains an egg — living, but not growing. 



