THE LAMARCKIAN THEORY 425 



of evolution. It is fifty j^ears older than Darwin's theory, yet it 

 bobs up like a specter even today. In spite of the vigorous opposi- 

 tion of the Darwinian school of thought and the fact that the 

 inheritance of ac(iuired characters is devoid of sound proof, we 

 must recognize that many l^iologists have such a favorable attitude 

 toward it that they would be glad to see it proved, or at least 

 given as sound a basis for acceptance as the germinal theories of 

 evolution. 



It is significant that this condition can exist. Science is not 

 prone to cling to useless theories when once a question is settled, 

 hence this situation is very suggestive. When we consider all of 

 the theories advanced to explain evolutionary processes, we find 

 that none of them is adequate. Natural selection is logical and 

 is commonly accepted as a factor in evolution, but as originally 

 stated it meets a serious oljstacle as an explanation of species- 

 formation. The mutation theory obviously explains many changes 

 in organisms, and supplies a valuable corollary for natural selec- 

 tion. In minute mutations we may well have the permanent 

 modifications for natural selection to perpetuate in the gradual 

 differentiation of species, but if we accept this as an adequate 

 explanation of species-formation we must then explain the occur- 

 rence of mutations. They are due to chromosomal modification, 

 but what modifies the chromosomes? Are all such changes hap- 

 hazard? Is the wonderful adjustment of organisms to their 

 environment entirely due to the selection and preservation of 

 random characters? Reason seems to tell us that there is more 

 to the story than this. A satisfactory explanation is not yet 

 available but the very persistence of the Lamarckian idea leads 

 us to consider evolutionary processes with open minds. Partisan 

 views and investigations have failed to attain the desired end, 

 and in their failure we may find a lesson for modern evolution. 



Summary. Lamarck's theory of evolution was first stated in 

 1809 as two laws, known as the law of use and disuse and the law 

 of inheritance of acquired characters. Laws which he stated 

 later are of no moment. Of these two fundamental laws, use and 

 disuse is now commonly known to have an effect upon individual 

 development, but the inheritance of characters produced in this 

 way has never been demonstrated. For many centuries the idea 

 has been accepted by some individuals without proof. JNIany 

 biologists have also favored it, and have accumulated evidence 



