THE LAMARCKIAN PRINCIPLE 63 



web tends to turn the feather on its axis, and force the 

 inner side upward, pressing it closely against the feather 

 next to it. The same contrivance rounds the tail and makes 

 it useful as a parachute. I say nothing about the marvellous 

 interlocking of the barbs. 1 No further description is wanted 

 to show that the feathers are as perfect as the muscles 

 that move the wings. How can we believe, then, that the 

 feathers have been handicapped by being debarred from a means 

 of progress which has been available for the muscles ? 



I will briefly mention here what has been urged by an 

 enthusiastic Lamarckian on the subject of feathers. Though 

 they are themselves dead structures, yet they spring from 

 papillae in the skin and are moved by muscles which move 

 the skin. Birds which display their plumes have, he maintains, 

 developed them through exercise. The peacock's enormous 

 tail-coverts have resulted from his constant habit of displaying 

 them ! This is Lamarckism run wild. It is enough to say that 

 if exercise were the cause of a feather's growth, then the eagle's 

 great remiges, that do a thousand times as much work as the 

 peacock's plumes, would never have had their outer web reduced 

 as it is, and the peacock's dowdy and comparatively short tail 

 feathers that support and help to move the lordly tail coverts 

 would have been very different from what they are, were 

 exercise of the associated muscles all that is required to pro- 

 duce nobility of plumage. 



When Weismann has been worsted in controversy it has often Repro- 

 been through the cumbersomeness of his own armour rather i u s c t 

 than the skill of his adversaries. Notably has this been so when, 

 arrayed in his elaborate panoply of biophors, determinants, ids, 

 idants, he has tried a tilt with them on the much-vexed question 

 of the reproduction of lost parts. When a cray-fish loses a claw, 

 he proceeds to grow another. The salamander is celebrated for 

 its power of replacing lost limbs. How explain this, he is asked, 

 if the germ-plasm lives apart ? Then appear the armies of 

 determinants that he has called into being and he marshals 

 them, each in its place, not without difficulty. This I cannot 



1 I have described this in my Structure and Life of Birds, pp. 147-149. 



