374 THE HISTORY AND SCOPE OF ZOOLOGY IX 



consideration of certain classes of facts which seem 

 to favour the Lamarckian hypothesis, but also by a 

 respect for the general prejudice in its favour and for 

 Mr. Herbert Spencer's authority, was of the opinion 

 that acquired characters are in some cases transmitted. 

 It should be observed, however, that Darwin did not 

 attribute an essential part to this Lamarckian hypo- 

 thesis of the transmission of acquired characters, 

 but expressly assigned to it an entirely subordinate 

 importance. 



The new attitude which has been taken since 

 Darwin on this question is to ask for evidence of this 

 asserted transmission of acquired characters. It is 

 held^ that the Darwinian doctrine of selection of 

 fortuitous couQ-enital variations is sufficient to account 

 for all cases, that the Lamarckian hypothesis of trans- 

 mission of acquired characters is not supported by 

 experimental evidence, and that the latter should 

 therefore be dismissed. Weismann has also ingeni- 

 ously argued from the structure of the egg-cell and 

 sperm-cell, and from the way in which, and the period 

 at which, they are derived in the course of the growth 

 of the embryo from the egg — from the fertilisad 

 egg-cell — that it is impossible (it would be better 

 to say highly improbable) that an alteration in 

 parental structure could produce any exactly repre- 

 sentative change in the substance of the germ or 

 sperm-cells. 



It does not seem improbable that the doctrine of 

 organic evolution will thus become pure Darwinism 



^ Weismann, Vererhung, etc. 1886. 



