THE INDIVIDUAL AND THE SPECIES 181 



and germinal cells. Neglecting these results in the 

 meantime, we see that the germ-cells contain within 

 themselves the potentiality of reproducing the entire 

 organism in all its specificity. That which is trans- 

 mitted from the parent to the offspring is the parental 

 organisation in all its specificity ; and to say that this 

 organisation is a material thing is, of course, to state 

 a hypothesis, not a fact of observation. 



This transmission of a specific form and mode of 

 behaviour from generation to generation is what a 

 hypothesis of heredity attempts to explain — that is, to 

 describe in the simplest possible terms, making use 

 of the concepts of physical science. " Twelve years 

 ago," says Jacques Loeb, " the field of heredity was 

 the stamping ground for the rhetorician and meta- 

 physician ; it is to-day perhaps the most exact and 

 rationalistic part of biology, where facts cannot only 

 be predicted qualitatively, but also quantitatively." 

 Let the reader examine for himself the meagre array 

 of facts on which this apotheosis of mechanistic biology 

 is based. 



Two modern hypotheses of heredity demand atten- 

 tion — Weismann's hypothesis of the continuity of the 

 germ-plasm, and Semon's " Mnemic " hypothesis. In 

 the latter it is assumed that the basis of heredity is 

 the unconscious memory of the organism : modes of 

 functioning are " remembered " by the germ-plasm 

 and are transmitted. This notion presents many points 

 of similarity to that which we consider later on, so 

 that it need only be mentioned here. Weismann's 

 hypothesis — like Darwin's hypothesis of Pangenesis — 

 is a corpuscular one, and has obviously been sug- 

 gested by the modern development of the concepts of 

 molecules and atoms in the physical sciences. It 

 supposes that that which is handed down is a material 



