THE THEORY OF DESCENT 279 



perhaps of a rather simple explanation, as in fact has been 

 suggested. Some necessary means both of inheritance and 

 of morphogenesis, the former being present in the propaga- 

 tion cells, may be said to have been changed or destroyed 

 by heat, and therefore, what seems to be inherited after 

 the change of the body only, would actually be the effect 

 of a direct influence of the temperature upon the germ 

 itself. 1 Let me be clearly understoood : I do not say that 

 it is so, but it may be so. What seems to me to be more 

 important than everything and to have a direct bearing on 

 the real discovery of the inheritance of acquired characters 

 in the future, is this. In some instances plants which 

 had been forced from without to undergo certain typical 

 morphological adaptations, or at least changes through 

 many generations, though they did not keep the acquired 

 characters permanently in spite of the conditions being 

 changed to another type, were yet found to lose the acquired 

 adaptations not suddenly but only in the course of three or 

 more generations. A certain fern, Adiantum, is known to 

 assume a very typical modification of form and structure, if 

 grown on serpentine ; now Sadebeck, 2 while cultivating this 

 serpentine modification of Adiantum on ordinary ground, 

 found that the first generation grown in the ordinary 

 conditions loses only a little of its typical serpentine 

 character, and that the next generation loses a little more, so 

 that it is not before the fifth generation that all the characters 

 of the serpentine modification have disappeared. There are 



i 1 Of course the inheritance of specific values from the results of fluctuating 

 variations, leading to new averages of variability (see p. 265), may also be 

 understood in this manner, the conditions of nourishment acting upon the 

 adult and upon its germs equally well. 



2 Bcrickte iib. d. Sitzung. d. Ges. f. But., Hamburg, 1887, 3 Heft. 



