VI PREFACE. 



lines we have suggested, then, in short, it did." That is the sum 

 of our argument. 



Were we all agreed in our assumptions and as to the canons of 

 interpretation, there might be some excuse, but we are not agreed. 

 Out of the same facts of anatomy and development men of equal 

 ability and repute have brought the most opposite conclusions. 

 To take for instance the question of the ancestry of Chordata, the 

 problem on which I was myself engaged, even if we neglect 

 fanciful suggestions, there remain two wholly incompatible views 

 as to the lines of Vertebrate descent, each well supported and 

 upheld by many. From the same facts opposite conclusions are 

 drawn. Facts of the same kind will take us no further. The 

 issue turns not on the facts but on the assumptions. Surely we 

 can do better than this. Need we waste more effort in these vain 

 and sophistical disputes ? 



If facts of the old kind will not help, let us seek facts of a new 

 kind. That the time has come for some new departure most 

 naturalists are now I believe beginning to recognize. For the 

 reasons set forth in the Introduction I suggest that for this new- 

 start the Study of Variation offers the best chance. If we had 

 before us the facts of Variation there would be a body of evidence 

 to which in these matters of doubt we could appeal. We should 

 no longer say " if Variation take place in such a way," or " if such 

 a variation were possible ; " we should on the contrary be able to 

 say " since Variation does, or at least may take place in such a way," 

 " since such and such a Variation is possible," and we should 

 be expected to quote a case or cases of such occurrence as an 

 observed fact. 



To collect and codify the facts of Variation is, I submit, the 

 first duty of the naturalist. This work should be undertaken if 

 only to rid our science of that excessive burden of contradictory 

 assumptions by which it is now oppressed. Whatever be our 

 views of Descent, Variation is the common basis of them all. As 

 the first step towards the systematic study of Variation we need a 

 compact catalogue of the known facts, a list which shall contain as 

 far as possible all cases of Variation observed. To carry out such a 

 project in any completeness may be impossible ; but were the plan 

 to find favour, there is I think no reason why in time a consider- 

 able approach to completeness should not be made. 



