HEREDITY AND EVOLUTION 99 



decide whether all the ascertained facts agree with it, 

 and can be explained by it. 1 



Whatever may be the ultimate verdict on this bold 

 hypothesis, the value of Weismann s work is such 

 as must largely influence thought as to the perplexing 

 problems involved. Little can be done here beyond 

 stating difficulties which seem still to hang over 

 the question, and showing some appreciation of the 

 suggestiveness of what has been written. Darwin is 

 strong in his array of natural history evidence for 

 transmission of acquired variations. If that evidence 

 be carefully considered, it will seem impossible to 

 deny that acquisitions of one generation reappear in 

 the next. There is an array of facts which clearly 

 establish the conclusion. To the force of this testi 

 mony, theories of the life-history of germ-plasm must 

 yield. On the same ground, the theory of Evolution 

 by natural selection is sustained. Natural law pro 

 vides for organic advance, and with this must be 

 included heredity, securing continuity of useful acquisi 

 tions. When, however, we turn to Darwin s theory of 

 pangenesis, it seems impossible to extend to it the 

 same accep nee. To suggest that the result is secured 

 by all the ceils of the parent body sending gemmules 

 or germs representative of their distinctive character 

 to be assimilated and absorbed in the individual germ- 

 cell, is to present a hypothesis too cumbrous, too 

 mechanical, too much out of line with the analogies 

 of cell development, now well ascertained. That a 

 cell, only a small fraction of an inch in diameter 

 and even the microscopic nucleus within that cell 

 should be the germ of the most elaborate organism, is 



1 Essays upon Heredity, vol. i. p. 1 76. 2 Vide p. 95. 



