Chapter II 



THE SIGNIFICANCE OF THE CHEMICAL MOLECULES OP 



THE PROTOPLASM WITH REFERENCE TO THE 



THEORY OF HEREDITY 



I. Introduction 



According to our present conception of all nature, the 

 wonderful phenomena of heredity must have a material 

 basis, and this basis can be no other than the living pro- 

 toplasm. Every cell originates through the division of 

 one that already exists ; the living substance of the 

 mother-cell is distributed among the individual daughter- 

 cells and passes into them with all its hereditary qualities. 

 Microscopic investigation of the cell-body and the art of 

 the breeder, so far apart from each other until recently, 

 come nearer and nearer to working hand in hand. And it 

 is only through the co-operation of these two great lines 

 of human thought that we can succeed in establishing the 

 basis for a theory of heredity. 



Chemistry teaches us that living protoplasm, like any 

 other substance, must be built up of chemical molecules, 

 and that a final explanation of the phenomena of life can 

 be reached only when we shall succeed in deriving the 

 processes in protoplasm from the grouping of its mole- 

 cules, and from the composition of the latter out of their 

 atoms. 



We are still, however, very far from this goal. The 

 chemists study chiefly pure bodies, that is, such as are 

 built up from like molecules; but protoplasm is evidently 

 a mixture of numerous, if not of almost countless differ- 

 ent chemical compounds. And by far the most of these 



