TRANSMISSION OF ACQUIRED CHARACTERS. 411 



he merely proves that he does not understand what I have said 

 upon the subject. In what other way could the transformation 

 of species be produced, if changes in the germ-plasm cannot be 

 transmitted ? And how could the germ-plasm be changed except 

 by the operation of external influences, using the words in their 

 widest sense ; unless indeed we assume with Nageli, that changes 

 occur from internal causes, and imagine that the phyletic develop- 

 ment of the organic world was planned in the molecular structure 

 of the first and simplest organism, so that all forms of life were 

 compelled to arise from it, in the course of time, and would have 

 arisen under any conditions of life. This is the outcome of Nageli's 

 view, against which I have contended for years. 



If we now use the term ' acquired characters ' for changes in the 

 soma which, like spontaneous abnormalities, depend upon previous 

 changes in the germ-plasm it is of course easy to prove that 

 acquired characters are transmitted ; but this is hardly the way to 

 advance science, for nothing but confusion would be produced by 

 such a use of terms 1 . I am not aware that any one has ever 

 doubted that spontaneous characters, such as extra fingers or toes, 

 patches of grey hair, moles, etc., can be transmitted. It is true 

 that such characters are sometimes called ' acquired ' in pathological 

 works, but His has rightly insisted that such an obviously inaccurate 

 use of the term ought to be avoided, in order to prevent mis- 

 understanding. If every new character is said to be ' acquired ' 



1 Compare a paper by J. Orth, 'Ueber die Entstehung und Vererbung indi- 

 vidueller Eigenschaften,' Leipzig, 1887. This author considers my theory of the 

 non-transmission of acquired characters to be incorrect, because he will insist upon 

 using the term ' acquired ' for those characters which are due to spontaneous changes 

 in the germ ; although he considers that they are only indirectly acquired. He also 

 reproaches me with not having discriminated with sufficient clearness between the 

 two modes in which new characters are acquired by the body, and with having 

 altogether failed to take into account the class of characters which are due to 

 variations in the germ. On the very same page he quotes the following sentence 

 from my writings : ( Every change of the germ-plasm itself, however it may have 

 arisen, must be transmitted to the following generation by the continuity of the 

 germ-plasm ; and hence also any changes in the soma which arise from the germ- 

 plasm must be transmitted to the following generation.' Not only does the trans- 

 mission of Orth's ' indirectly acquired characters ' necessarily follow from this sen- 

 tence, but it is even distinctly asserted by it. I cannot understand how any one 

 who is aware of what happened at the meeting of the Association of German 

 naturalists at Strassburg in 1885, can charge me with the confusion of ideas which 

 has prevailed since Virchow took part in the discussion of this question. 



