TRANSLA TOR 'S PREFA CE 



therefore been increased in the kitten, although the action of 

 " sexual combination " is entirely excluded. 



Again, another of the assumptions on which Weismann 

 builds is that " everything depends on adaptation." He 

 confesses himself that this is a conviction of his own, not a 

 demonstrated truth. In fact, it is obviously an assumption 

 necessary to the main proposition of his theory. For Weis- 

 mann means to say that every part of every animal, every 

 structural relation, is either an advantage to its possessor 

 under the present conditions of its life, or was once an 

 advantage to its ancestors. No feature or character which 

 was not at one time or other of advantage to its possessor 

 in the struggle for existence could have been selected. 

 Therefore, if some things were not adaptations, congenital 

 variation and natural selection could not be the necessary 

 and sufficient explanation of organic evolution, as Weismann 

 and his disciples maintain them to be. 



It is evident, on Weismann's own admission, that it has 

 not yet been proved that everything is adapted, that is, that 

 every character or structural feature in every animal has its 

 use in the struggle for existence. It is a mere supposition, 

 therefore, that everything has been selected. In direct 

 opposition to Weismann, I am prepared to maintain, first, 

 that many structural features can be pointed out which are 

 not useful to their possessors ; and secondly, that all adapta- 

 tions are due to the inheritance of acquired characters. 



What is the use of the coiling of the shell and the torsion 

 of the organs in the greater number of Gasteropods ? Professor 

 Lankester has admitted recently in the pages of Nature that 

 he has been teaching for many years that this torsion was 

 due to a mechanical cause, namely, the weight of the shell 



