On the Mechanical Conception of Nature. 667 



same cause he cannot assume for the one a 

 causal power and for the other a directive 

 principle. If nutrition and cell-multiplication are 

 purely mechanical processes, so also is heredity. 

 Although it has not yet been possible to demon- 

 strate the mechanism of this phenomenon, it can 

 nevertheless be seen broadly that by means of a 

 minimum of living organic matter (e.g. the proto- 

 plasm of the sperm and germ-cell) certain motions 

 are transferred, and these can be regarded as 

 directions of development, as I have already 

 briefly laid down in a former work." The power 

 of organisms to transmit their properties to their 

 offspring appears to me to be only conceivable in 

 such a manner " that the germ of the organism 

 by its chemico-physical composition together with 

 its molecular structure, has communicated to it a 

 fixed direction of development the same direc- 

 tion of development as that originally possessed 



by the parental organism " (foe. cit. p. 



24). This is confessedly nothing more than a 

 hint, and we do not leam therefrom the means by 

 which developmental direction can be possibly 

 transferred to another organism. 



Recently Haeckel, that indefatigable pioneer to 

 whom we are indebted for such a rich store of 

 new ideas, has attempted to bridge over this gap 

 in his essay on " The Perigenesis of the Plasti- 



11 " Uber die Berechtigung der Darwin'schen Theorie," 

 Leipzig, 1868. 



X x 



