54 CRITICISM OF MECHANISTIC THEORY 



duction and heredity. This vast organisation 

 of cell-mechanisms has all been developed 

 from a single cell, itself the product of the 

 union of two cells an ovum and a sperma 

 tozoon ; and we have every reason to believe 

 that the hereditary characters, which are 

 derived through both cells, are carried in the 

 two nuclei which unite to form the nucleus 

 of the fertilised germ-cell. On the mechan 

 istic theory this nucleus must carry within 

 its substance a mechanism which by reaction 

 with the environment not only produces the 

 millions of complex and delicately balanced 

 mechanisms which constitute the adult organ 

 ism, but provides for their orderly arrange 

 ment into tissues and organs, and for their 

 orderly development in a certain perfectly 

 specific manner. 



The mind recoils from such a stupendous 

 conception ; but let us follow the argument 

 further. In the previous lecture I gave such 

 an account of heredity as is usually given 

 from the mechanistic standpoint. It needs 

 very little consideration to see that this 

 account consisted of little more than empty 

 words. The germ-plasm was supposed to be 



