LECTUKE XII 

 INTRA- SELECTION OR SELECTION AMONG TISSUES 



Does tho Laniarckian principle really play a part in the transformations of 

 species? — Darwin's position in regard to tliis question — Doubts expressed by Galton 

 and others — NeoLaniarckians and Neo-Darwinians — Results of exercise and practice: 

 functional adaptation— Wilhelm Roiix, Kamjaf der Theile. 



We have devoted a whole series of lectures to studying the 

 Darwin- Wallace principle of Natural Selection and the range of its 

 operation. It seemed to us to make innumerable adaptations intel- 

 ligiltlc up to a certain point. We now understand how the purpose- 

 fulness, which we meet with everj'^where among organisms, can have 

 arisen without the direct interference of a Power working intentionally 

 towards an end — simply as the outcome and result of the survival 

 of the fittest. The two forms of the processes of selection, ' natural 

 selection ' in the narrower sense, and ' sexual selection,' dominate, so 

 to speak, all parts and all functions of the organism, and are striving 

 to adapt these as well as possible to the conditions of their life. And 

 although the range of operation of Natural Selection is ineomparabh' 

 greater, because it actually afiects every part, yet we must attribute 

 to sexual selection also, at least among animals, a range of influence 

 by no means unimportant, since through it, as far as we can see at 

 present, not only do the secondary sexual characters in all their 

 diversity arise, but b}^ the transference of these to the other sex that 

 too is modified, and thus the whole species may be influenced, and 

 may indeed be started afresh on an unlimited series of further trans- 

 formations. 



But although the processes of selection play such an important 

 part in the transformations of the forms of life, we have to inquire 

 whether they are the sole factors in these transformations, whether 

 the accumulation of chance variations in the direction of utility has 

 been the sole factor in bringing about the evolution of the animate 

 world, or whether other factors have not also co-operated with it. 



We are all aware that Lamarck regarded the direct influence of 



use and disuse as the most essential factor in transformation, and that 



^ Darwin, though hesitatingly and cautiousl}^ recognized and accepted 



this factor, Avhich he believed to be indispensable. Indeed, it seems 



