it FORM AND GROWTH 23 



is exposed to different external influences, therefore there 

 results, as a quite self-evident consequence of physico- 

 chemical change in the organism, difference of growth, and 

 therewith, of the shape and form. 



Just as in inorganic nature from different mother lyes 

 different crystals separate, as even simple mechanical shock 

 can produce dimorphous crystallisation, so crystallise, if I 

 may so express myself, in the course of ages, organic forms, to 

 a certain degree different, out of the same original mass. 

 Only the organism works with much more complex material, 

 with a much greater variety of compounds. The greater 

 delicacy and multiplicity of the organic processes determine 

 other and more manifold forms in the organic world. 



But just because the form of the organism depends upon 

 physico-chemical processes, it is like the form of the inorganic 

 crystal, a definite one, and can, when modification takes place, 

 only change in certain definite directions. 



When such new characters, which are simply to he referred 

 to changed growth, become persistent in a group of individuals 

 by constant and still continuing inheritance, and when this 

 group in any way whatever has lost its connection with the 

 rest of its relatives, by the loss of the intermediate forms, then 

 we speak of a species. 



New, changed form -constituents appear therefore in the 

 variety and species as the expression of changed growth. 



In other words, the origin of species obeys exactly the 

 same laws as simple growth ; it is the consequence of un- 

 ending dissimilar growth of the organic world taking place 

 under changed conditions, with the postulate of permanent 

 separation of dissimilar links of the growing chain of this 

 organic world. 



Eeproduction and individual development likewise depend 

 upon the laws of growth. 



