GENERAL ARGUMENT AGAINST 197 



p. 168). And besides fictitious cases there are some puzzling 

 phenomena, which the supporters of the negative position are 

 wont to dismiss as " coincidences " — which, it must be con- 

 fessed, is never a very satisfactory way of dealing with difficult 

 cases. 



§ 7. General Argument against the Transmissibility of 

 Modifications 



Most of the evidence brought forward in support of the belief 

 in the inheritance of acquired characters is terribly anecdotal ; 

 but apart from this Weismann was led to a position of entire 

 scepticism by his realisation of the continuity of the germ- 

 plasm. 



The Apartness of the Germ-cells.— If the germ-plasm or the 

 material basis of inheritance be something relatively apart from 

 the body, and from its everyday metabolism, something often 

 segregated at a very early stage in development, there is a 

 presumption against its being readily affected in a specific 

 manner by detailed exogenous changes wrought on the structure 

 of the body. 



It seems accurate to say that the reproductive cells which 

 have the potentiality of becoming offspring never arise from 

 differentiated body-cells. Whether they are recognisable as 

 such, late or early, the germ-cells are simply those cells which 

 retain in all its integrity the complex, definite, and stable organi- 

 sation of the fertilised ovum from which the whole organism 

 develops. They have their power of reproducing creatures 

 more or less like the parents just because they are continuous, 

 through an unspecialised cell-lineage, with the fertilised ovum 

 from which the parental body arose. All the somatic cells are, 

 of course, Ukewise the progeny of the fertilised ovum, but in their 

 lineage there are differentiation and specialisation. We imagine 

 that in them the numerous items or potentialities in the fertilised 



