ii 4 THEORIES OF EVOLUTION 



organism. Its nervous and muscular mechanism is so 

 arranged that mutilation actually stimulates it to contract, 

 and it continues to hold the enemy. In the case of 

 certain crabs, the dismembered claws keep snapping and 

 jumping about. The same is true of the tails of many 

 lizards, which, when thrown off, will jump about in the most 

 active way, distracting the attention of the enemy, while the 

 lizard makes its escape. Here, too, mutilation stimulates 

 the nervous and muscular mechanism in claw and tail. 



In these cases of actively used parts of the organism 

 the Lamarckian interpretation is absolutely at fault. 

 You cannot apply it. It is impossible to explain upon 

 the theory of the transmitted effects of use and disuse. 

 No activity manifested by the tail after it has ceased to 

 be part of the lizard can ever be transmitted. Not only 

 that, but it is difficult to see how the development under- 

 gone by the tail from the effects of use and disuse, &c, 

 up to the time of its severance, can be hereditary. And 

 so with the claw. The large claws are the most im- 

 portant appendages of the lobster, and yet it is certain 

 that many a lobster loses one of these organs and grows 

 a new one, several times in the course of its life. We 

 have here a very specialized organ with definite functions 

 which continue in even an increased degree after severance 

 from the animal : all this is readily explained by the 

 Darwinian Theory, but cannot be explained by the 

 Lamarckian. 



The same inadequacy of the Lamarckian Theory is 

 forced upon us when we examine a little more deeply 

 into the nature of the process which is supposed to occur. 

 The Lamarckians attempt to explain joints and some 

 other structures by the effects of stress and pressure, but 

 when we look into the matter we find that the explanation 

 is not so complete as it is supposed to be. 



For instance, it has been believed in the United States 

 by many distinguished biologists that the complex shape 

 of mammalian teeth is due to pressure produced by 

 mastication. As the pressure has been applied to the 

 tooth, so has the tooth grown. But would pressure 

 produce such an effect upon a tooth ? That is certainly 



