Characters, Hereditary and Acquired. 131 



terrestrial and aerial stems to grow underground and in water : 

 the structures at once began to assume the subterranean or 

 aquatic type, as the case might be; and, conversely, aquatic 

 plants made to grow upon land at once began to assume the 

 terrestrial type of structure, while analogous results followed 

 changes from a subterranean to an aerial position, and vice 



This is also quoted from the Rev. Prof. Henslow's 

 letters to me, and the important point in it is, that 

 the great changes in question are proved to be of 

 a purely " somatogenetic " kind ; for they occurred '• at 

 once ■" in the ready-grown plant, when the organs 

 concerned were exposed to the change from aquatic 

 to terrestrial life, or vice versa — and also from a sub- 

 terranean to an aerial position, or vice versa. Con- 

 sequently, even the abstract possibility of the changed 

 conditions of life having operated on the seed is here 

 excluded. Yet the changes are of precisely the same 

 kind as are now hereditaiy in the wild species It 

 thus appears undeniable that all these remarkable and 

 uniform changes must originally have been somato- 

 genetic changes ; yet they have now become blasto- 

 genetic. This much, I say, seems undeniable ; and 

 therefore it goes a long way to prove that the non- 

 blastogenetic character of the changes has been due 

 to their originally somatogenetic character. For. if 

 not, how did natural selection ever get an opportunity 

 of making any of them blastogenetic, when every 

 individual plant has always presented them as already 

 given somatogenetically ? This last consideration 

 appears in no small measure to justify the opinion of 

 Mr. Henslow, who concludes — "These experiments 

 prove, not only that the influence of the environment 



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