CHAPTER VII 



RECENT ADVANCES AND THE PRESENT STATE OF 

 KNOWLEDGE CONCERNING THE MODIFICATION OF 

 THE GERMINAL CONSTITUTION OF ORGANISMS BY 

 EXPERIMENTAL PROCESSES 



INTRODUCTION 



Through inheritance there comes the rhythmic repeti- 

 tion in each specific organic form of a precise and definitely 

 repeated series of events ending in the production of an 

 individual which in time sets free from itself a highly organ- 

 ized and specific mass — a gamete, which, when properly 

 combined with some other gamete and nurtured, repeats 

 again the series of events which took place in the parent 

 bodies which preceded them. Throughout all of this com- 

 plex, rhythmic process a material basis, the germ plasm, 

 keeps intact from parent to progeny genetic lines of descent. 

 This continuity of material basis — ^first clearly recognized 

 by Gustav Jaeger, and later woven by Weismann into his 

 germ-plasm theories — while known in its gross appear- 

 ance and many of its behaviors, is nevertheless quite 

 unknown as regards its real constitution and the means 

 through which it does reproduce so accurately in each 

 generation the sequence of events characteristic of its 

 specific organic form. 



The purely a-priori hypotheses of the "constitution" 

 of this substance in reality help us little or not at all as a 

 basis for experimental investigation. The id-determinant- 

 biophore fabric of Weismann, Naegeli's micellae chains, 



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