xlvi INTRODUCTION 



striking instance of this tendency when I come to deal with 

 his physiology ; for in physiology it led him to views much 

 more conspicuously erroneous than it did in zoology ; yet 

 we shall find it still harder to condemn him for this particular 

 paralogism in physiology, since there are a few physiologists 

 even at the present day (as I shall show) who are addicted 

 to false reasoning of a similar kind. 



That Lamarck should have believed in the inheritance of 

 acquired characters was, indeed, almost inevitable. Not 

 only so, but the invention of this hypothesis was a very 

 remarkable and honourable achievement. Before a true 

 theory is discovered, the usual routine is for many hypo- 

 theses to be invented and tested. The discovery of a true 

 hypothesis is only effected after the rejection of a multitude 

 of false hypotheses. The invention of a hypothesis such as 

 the inheritance of acquired characters required a genius of 

 no ordinary kind : had it not been for this invention, bio- 

 logists might not yet have reached a knowledge of the great 

 importance attaching to the discrimination between acquired 

 and congenital characters. Consider how the facts must 

 have presented themselves to Lamarck. He saw that all 

 progeny possess a structure closely resembling that of their 

 parents : he saw that when one of the parents possessed some 

 striking feature, not peculiar to its species, some variation 

 in short, that variation was very commonly transmitted 

 to the offspring ; once again, he saw that use or disuse of 

 any part by an individual affected the structure of that 

 part in that individual, causing it to increase or diminish 

 in physical size and capacity, so as to produce a variation 

 from the normal, not distinguishable by any external examina- 

 tion from the congenital variations. Is it not then perfectly 

 natural that he should have assumed such acquired variations 

 to be inheritable ? What possible grounds can he have had 

 for supposing that variations from the normal are of two 

 utterly different kinds, one of which is capable of being 

 inherited, while the other is not ? Is not this just one of 

 those traps which, as Darwin remarked, nature seems to 



