PURITY OF THE GERM CELLS 75 



The minute study of the germ-cells, taken in connec- 

 tion with modern experimental work on the methods 

 by which inheritance takes place* shows a strong 

 tendency to confirm Weismann's view, so far as the case 

 of distinct and definite characters is concerned. But 

 if we regard such definite characters as having arisen 

 by definite steps or mutations according to the view 

 now gaining ground, the study of them will have no 

 bearing upon the question of use-inheritance, since 

 use does not lead to large and definite changes in the 

 individual* but to comparatively small changes of a 

 quantitative kind. 



There are some t including de Vries, who regard all 

 fluctuating variations (individual differences) as being 

 of the nature of acquired characters, and as being at 

 the same time capable of hereditary transmission, 

 although de Vries believes the amount of progress 

 possible in this way to be strictly limited. Let us see 

 if there is any way in which a transmission of such 

 characters can be conceived of. 



It must be pointed out that the cells which make 

 up an organism are not completely marked off and 

 separated from one another ; on the contrary, it seems 

 impossible to doubt that reactions may take place 

 between them long after their first formation. Indeed* 

 Sedgwick has shown that in a number of diverse kinds 

 of animals there is never any sharply limiting barrier 

 between cells at all, and this writer has gone so far as 

 to speak of animals in general as being built up of a 

 continuous network of protoplasm with nulcei at the 

 nodes. In plants, too, though at first sight their con- 



