54 'WHAT IS A SPECIES?' 



instances will be drawn from the Lepldoptera rather 

 than other Orders of insects, because of the numberless 

 examples of subtle distinction between forms which but 

 yesterday, so to speak, became separate ; because of our 

 knowledge, insufficient but considerable, of their geo- 

 graphical range ; because of our experience, excessively 

 imperfect and scanty, but still much larger than in other 

 Orders, of interbreeding and of descent from parent to 

 offspring. 



The Linnaean Conception of Species as Separately Created, 

 and Fixed for all time at their Creation. 



First among the attempts to define species must be 

 placed that which we rightly associate with the name of 

 Linnaeus : — ' Species tot sunt, quot diversas formas ab 

 initio produxit Infinitum Ens, quae formae, secundum 

 generationis inditas leges produxere plures, at sibi semper 

 similes.' 



It is necessary at the outset to point out that the 

 Linnaean definition contains two widely different ideas. 



First, species are diver sae formae, distinguished from 

 one another by characters which can be studied and de- 

 fined. Secondly, these specific differences were originally 

 created as we see them, and are for ever permanent and 

 fixed. 



I propose to discuss the second idea before the first. 



It has been admirably pointed out by the late Rev. 

 Aubrey L. Moore, 1 that the dogma of the fixity of 

 species is entitled to none of the respect which is due to 

 age. ' It is hardly credible to us,' he wrote, ' that Lord 

 Bacon, " the father of modern science " as he is called, 

 though he was only a schoolman touched with empiricism, 

 believed not only that one species might pass into 

 another, but that it was a matter of chance what the 

 transmutation would be. Sometimes the mediaeval 

 notion of vivification from putrefaction is appealed to, as 

 where he explains the reason why oak boughs put into 

 the earth send forth wild vines, " which, if it be true (no 



1 Science and the Faith, London, 1889, pp. 174 et seq. 



