39 S THE GERM-PLASM 



of changes in the organism which is with difficulty explained 

 by the supposition of changes in the germ ; these consist 

 in modifications which appear as the direct consequence of 

 some alteration in the surroundings . But our knowledge on 

 this subject is still very defective, and we do not know the 

 facts with sufficient precision to enable us to pronounce a final 

 verdict as to the cause of such changes.' Mention was then 

 made of a few of the large number of cases which have been 

 repeatedly quoted, and I attempted to show that none of them 

 stood criticism, that they could not be explained in the way some 

 investigators supposed, and that somatogenic variations are 

 only apparently hereditary ; for in reality a change must first be 

 brought about in the germ-plasm by the influence of the surround- 

 ings before such a variation can be produced. I then continued : 

 — 'It must be admitted that there are cases, such as the climatic 

 varieties of certain butterflies, which raise some difficulties against 

 this explanation. I myself, some years ago, experimentally in- 

 vestigated one such case, and even now I cannot explain the 

 facts otherwise than by supposing,' as I did then, that somatic 

 variations were transmissible. ' It must be remembered, how- 

 ever, that my experiments,' which have been repeated upon 

 several American species by H. W. Edwards, 'were not under- 

 taken with the object of investigating the question from this 

 point of view alone. New experiments, under varying con- 

 ditions, will be necessary to afl'ord a true explanation of this 

 aspect of the question,' * 



Since 1883 I have waited in vain for some skilled entomolo- 

 gist or for one of the numerous advocates of the transmission 

 of acquired characters, to carry out the proposed experiments. 

 In the meantime, as far as the time and material at my disposal 

 permitted, I have myself made a start on this line of research, 

 and now possess the results of a series of new experiments, 

 which, though not so numerous, complete, or exhaustive as I 

 could have wished, are nevertheless sufficient to form a more 

 trustworthy basis for a theory dealing with variations of this 

 kind. Some of these are described in the following section, a 

 more detailed account of them being left for another occasion. 



* Cf. my essay, ' Uber Vererbung,' Jena, 1883. English edition, Oxford, 

 1889, pp. 98-99. 



