62 THE LAMARCKIAN DOCTRINE 



therefore, that evolution proceeds entirely on lines of natural 

 selection. This emended doctrine has received the name of 

 ' Neo - Darwinian.' Often, however, it is termed simply the 

 'Darwinian,' though, as we see, Darwin did not hold it in its 

 entirety. 



94. The question as to whether acquirements are, or are not, 

 transmitted has been the subject of probably the most lengthened 

 and ardently debated of biological controversies. Prolonged 

 investigation, in the course of which the plant and animal kingdoms 

 were ransacked, failed to reveal a single convincing and unmistak- 

 able instance of the transmission of an acquirement. But though 

 the Lamarckian doctrine is abandoned by the majority of serious 

 students, it is worth while to devote some space to it, partly because 

 it is still an article of popular belief, partly because the study of 

 it will enable us to contrast it with the Darwinian theory and 

 so achieve a better understanding of what is meant by Natural 

 Selection, and partly because we shall thus early have an oppor- 

 tunity to demonstrate the importance of testing every speculation 

 by a rigorous deductive appeal to reality. 



95. The Lamarckian doctrine supposes that parental ' acquire- 

 ments ' tend to be ' inherited,' in however small a degree, by off- 

 spring. That is, it supposes that useful characters, which evolution 

 enables the parent to acquire as a response to use or injury, tend in 

 the child to betransmutedmto less adaptive characters, which develop 

 in response to the stimulus of nutriment. In the face of common 

 experience its scientific adherents did not maintain that the whole 

 of the parental acquirement was commonly ' inherited.' Thus, if 

 the tails of a pair of dogs were amputated, it was not thought 

 probable that the offspring would be born tailless, though it was 

 believed that this sometimes happened. It was thought merely 

 that some portion of the parent's loss tended to be ' inherited,' and 

 therefore, that if the mutilation were repeated during successive 

 generations, a race with diminished tails and ultimately a tailless 

 race would result. Again, it was not believed probable that, if a 

 man increased the size of his muscles by exercise, all of the increase 

 would be ' inherited,' but only some of it. In fact, it was main- 

 tained that acquirements were transmitted, as a rule, only ' faintly ' 

 and ' fitfully. 1 * 



96. Obviously the Lamarckian hypothesis professes to be a 

 theory both of heredity and evolution, the latter being an induction 

 from the former. As a theory of heredity it seeks to account for 



1 See Romanes, Darwin and after Darwin, vol. ii. p. 152. 



