404 ORGANIC GROWTH 



to use this phenomenon also as an argument against heredity. 

 Since a part of the body taken from the whole grows again 

 from the remainder is formed anew it is evident that it 

 is formed again notwithstanding the absence of all hereditary 

 connection between the lost part and its substitute. At the 

 same time he endeavours to give an explanation of recrescence 

 in the following fashion : l " When just what was lost is 

 replaced, it is clear that the newly-produced member does not 

 arise from a pre-existing germ of the member. The sectional 

 surface of the stump of the arm draws nutritive material to- 

 wards itself, and organises the molecules of that material into 

 an arm. The organising force is, however, a molecular force, 

 which cannot extend its influence from the living substance 

 of the stump to a distance, but acts only by attracting the 

 nutritive molecules which come within the sphere of activity 

 of the molecules of the stump, driving them into definite 

 positions, and so gradually produces a new living layer over 

 the exposed surface. The organisation of this new layer evid- 

 ently depends on the law of the organisation, i.e. of the 

 molecular arrangement and the chemical condition of the sur- 

 face over which the new layer is formed. The condition of 

 this layer is, in a word, the mathematically necessary con- 

 sequence of the condition of the older generating layer. But 

 since in the embryonic development this latter layer was also 

 in existence before that now reproduced arose, so this must 

 then have arisen in exactly the same way as it now arises for 

 the second time. Thus layer is formed upon layer, the 

 younger always the child of the older, until the organ is again 

 entire. The process of recrescence therefore consists in this, 

 that the exposed surface of the stump of the arm acts, as it is 

 always acting, on the molecules of the layer next to it, direct- 

 ing, arranging, organising them, so that every nutritive par- 

 ticle which comes within the region of that surface at once 

 1 Op. tit. pp. 65, 66. 



