VIII.] SUPPOSED TRANSMISSION OF MUTILATIONS, 437 



we shall obtain such proofs in future, for the cases are not of a 

 kind which lend themselves to an experimental investigation. 

 The hypothesis that acquired characters can be transmitted 

 is therefore only directly supported by the above-mentioned 

 instances of the transmission of mutilations. For this reason, 

 the defenders of the Lamarckian principle, who have come 

 forward in rather large numbers recently \ have endeavoured 

 to show that these observations are conclusive, and therefore of 

 the highest importance. For the same reason I believe that it is 

 my duty, as I take the opposite view, to explain what I think of 

 the value of these apparent proofs of transmitted mutilations. 



It can hardly be doubted that mutilations are acquired 

 characters : they do not arise from any tendenc}^ contained in 

 the germ, but are merely the reaction of the body under 

 external influences. They are, as I have recently expressed 

 it, purely somatogenic characters ^, viz. characters which 

 emanate from the body {soma) only, as opposed to the germ- 

 cells ; they are therefore characters which do not arise from 

 the germ itself. 



If mutilations must necessarily be transmitted, or even if 

 they might occasionally be transmitted, a powerful support 

 would be given to the Lamarckian principle, and the trans- 

 mission of functional hypertrophy or atrophy would thus 

 become highly probable. For this reason it is absolutely 

 necessary that we should try to come to a definite conclusion 

 as to whether mutilations can or cannot be transmitted. 



^ [One of the most remarkable forms of this revival of Lamarckism is 

 the establishment in America of a ' Neo-Lamarckian School,' which 

 includes among its members many of the most distinguished American 

 biologists. One of the arguments upon which the founders of the 

 school have chiefly relied is derived from the comparative morphology 

 of mammalian teeth. The evolution of the various types arc believed to 

 be due to modifications in shape, produced by the action of mechanical 

 forces (pressure and friction 1 during the life of the individual. The 

 accumulation of such modifications by means of heredity explains the 

 forms of existing teeth. 



It may be reasonably objected that the most elementary facts con- 

 cerning the development of teeth prove that their shapes cannot be 

 altered during the lifetime of the individual, except by being worn 

 away. The shape is predetermined before the tooth has cut the gum. 

 Hence the Neo-Lamarckian School assumes, not the transmission of 

 acquired characters, but the transmission of characters which the parent 

 is unable to acquire ! — E. B. P.] 



^ See p. 426 of the preceding Essay (VII). 



