112 THE CELL IN RELATION TO 



or the germ-cell as a whole, can be a storehouse of 

 specific and detailed somatic impressions which 

 cause the reappearance of similar somatic effects 

 in generations to come. 



Darwin's ingenious attempt to picture such a 

 process was a legitimate speculation, worked out 

 with a power and insight that should stir enthu- 

 siasm in even the most skeptical of critics. More 

 than this, it still remains, as I think, the only in- 

 telhgible hypothesis of the transmission of ac- 

 quired characters, as Darwin understood the 

 phrase. But it finds to-day little or no real sup- 

 port in the results of observation and experiment. 

 Attempts have been made to substitute for Dar- 

 win's migrating gemmules soluble internal secre- 

 tions — ^hormones or other substances — ^that are 

 produced by the various organs and transmitted 

 to the reproductive organs through the fluids of 

 the body. Heredity has been compared, and 

 with justice, to an " organic memory " ; and this 

 has been assumed to be a property of the organ- 

 ism as a whole, irrespective of the distinction be- 

 tween germ-cells and soma. It has been urged 

 that the heredity of acquired characters is more 

 readily conceivable if the increments of change 

 be small and extended through long periods of 

 time. Any or all of these things are possible; 

 but let us not deceive ourselves. Does any of 

 these assumptions really lessen the difficulty or 

 give us a clear mental picture of what must occur 

 if the heredity of acquired characters be a fact? 



