II 



'WHAT IS A SPECIES?' 



The Presidential Address read at the Annual Meeting of the Entomo- 

 logical Society of London, January 20, 1904. Reprinted from the 

 Proceedings of the Society, 1903, p. lxxvii. 



Revised and modified : several paragraphs added and several rewritten: 

 additional footnotes. 



The late Professor Max Miiller, in an eloquent speech 

 delivered at Reading in 1891, spoke of the necessity 

 of examining, and, as time passes by, re-examining the 

 meaning of words. He referred as an illustration to the 

 man at the railway station who taps the wheels with his 

 hammer, testing whether each still rings true or has 

 undergone some change that may mean disaster. In 

 almost the same way, the speaker maintained, a word 

 may slowly and unobtrusively change its meaning, be- 

 coming, unless critically tested to ascertain whether it 

 still rings true, a danger instead of an aid to clear think- 

 ing, a pitfall on the field of controversy. He then went 

 on to say, that Darwin had written a great work upon 

 the Origin of Species, and had never once explained 

 what he meant by the word Species. So decided an 

 utterance — the statement was made emphatically — ought 

 to have involved a careful and critical search through the 

 pages of the work that was attacked. However this 

 may be, it is quite certain that the search was unsuccess- 

 ful ; and yet a few minutes' investigation brought me 

 to a passage in which the meaning attached by the author 

 to the term Species is set down in the clear, calm, and 

 simple language which did so much to convince an 

 unwilling 1 world. 



Darwin is speaking of the revolution which the accept- 

 ance of his views will bring about. ' Systematists will 

 be able to pursue their labours as at present ; but they 

 will not be incessantly haunted by the shadowy doubt 

 whether this or that form be in essence a species. This 

 I feel sure, and I speak after experience, will be no slight 



