8o CREATIVE EVOLUTION CHAP. 



might reach the same conclusion simply by looking at 

 certain very curious facts of regeneration in one and 

 the same organism. If the crystalline lens of a Triton 

 be removed, it is regenerated by the iris. 1 Now, the 

 original lens was built out of the ectoderm, while the 

 iris is of mesodermic origin. What is more, in the 

 Salamandra maculata^ if the lens be removed and the 

 iris left, the regeneration of the lens takes place at 

 the upper part of the iris ; but if this upper part 

 of the iris itself be taken away, the regeneration takes 

 place in the inner or retinal layer of the remaining 

 region. 2 Thus, parts differently situated, differently 

 constituted, meant normally for different functions, are 

 capable of performing the same duties and even of 

 manufacturing, when necessary, the same pieces of the 

 machine. Here we have, indeed, the same effect 

 obtained by different combinations of causes. 



Whether we will or no, we must appeal to some inner 

 directing principle in order to account for this convergence 

 of effects. Such convergence does not appear possible in 

 the Darwinian, and especially the neo-Darwinian, theory 

 of insensible accidental variations, nor in the hypothesis 

 of sudden accidental variations, nor even in the theory 

 that assigns definite directions to the evolution of the 

 various organs by a kind of mechanical composition of 

 the external with the internal forces. So we come to 

 the only one of the present forms of evolution which 

 remains for us to mention, viz., neo-Lamarckism. 



It is well known that Lamarck attributed to the 

 living being the power of varying by use or disuse of 



1 Wolff, &quot;Die Regeneration der Urodelenlinse &quot; (Arch.f.Entwickelungs- 

 mechanik, i., 1895, pp. 380 ff.). 



2 Fischel, &quot;tiber die Regeneration der Linse&quot; (Anat. Anzeiger, xiv., 1898, 

 pp. 373-3 8 o). 



