Weismanris theory of Heredity (1891). 81 



plasm and the somatoplasm have always occupied 

 different spheres": the fact is, that the germ-plasm 

 may directly act upon the somato-plasm, both within 

 and beyond the limits of the same organism. 



Hitherto we have been considering certain very 

 definite facts, which seem to prove that the germinal 

 elements are able directly to affect the somatic-tissues. 

 We have next to consider such facts as seem to prove 

 the opposite side of a reciprocal relationship — viz., 

 that the somatic-tissues are able directly to affect 

 the germinal elements. 



And here there are two distinct lines of evidence 

 to be distinguished. 



Firstly, in certain cases — exceptional it is true, but 

 this does not signify — somatic-tissues have been found 

 capable of modifying the hereditary endowments of 

 germinal elements by means of simple grafting. This 

 line of evidence has also been disregarded both by 

 Weismann and his followers ; but it is nevertheless an 

 important one to consider. For, if it be the case 

 that the somatic-tissues of an organism A, by being 

 merely grafted on those of organism B, can so affect 

 the germinal elements of B as to cause their offspring 

 to resemble A — or, contrariwise, if the somatic-tissues 

 of A can thus act on B — then, although it may not 

 be properly said that any " acquired characters " have 

 been transmitted from A to the progeny of B, (or 

 vice versa,) such an a-sexual transmission of alien 

 characters, in its relation to the theory of germ-plasm, 

 is scarcely less awkward than are certain facts which 

 they appear to prove. 



Secondly, that acquired characters may be trans- 



G 



