254 Theories Treating of Inheritance 



several nerve centers and unites them by new nerve tracts 

 becoming always smoother. These new impressions and 

 tracts remain then unaltered in the same places in which 

 they were produced and it is just in their continuance 

 in the place of their origin that there must be sought the 

 reason of the always greater ease with which these 

 melodies are reawakened in our memory. When the 

 muscles of the hand become accustomed to producing a 

 musical exercise, the greater development of the muscles 

 and the greater complexity of the nervous co-ordinations 

 which connect them with the brain constitute well defined 

 material alterations which remain unaltered in the places 

 where they arise and make the exercise, at first difficult, 

 always easier. 



In the development of the organism on the contrary 

 the causes of the repetition each time of always the same 

 ontogenetic stages must reside in a single cell, the germ 

 cell. But this cell is not in any way the place in which 

 are produced the material alterations which were acquired 

 by the parent organism and handed over to the descend- 

 ants, like the stronger development of certain muscles, 

 the greater complexity of certain nervous co-ordinations 

 and other similar variations. Of the stronger develop- 

 ment of muscles, of the greater complexity of the nervous 

 co-ordinations which are produced in the parent organ- 

 ism, there remains absolutely nothing, in so far as they 

 represent alterations of muscles and nerves, in the little 

 particle of matter which is destined to produce the 

 descendants. 



Consequently the comparison of the two phenomena, 

 although certainly very suggestive, is not sufficient by 

 itself to afford in any way an explanation of ontogenetic 

 phenomena. 



