272 Mr Bernard, On the Unit of Classification 



formula will be found adequate. But it is now a question of 

 how best to carry out this indispensable preliminary sorting. 

 The higher orders are apparently fairly easy to sort out, and 

 being comparatively few in number, errors are lightly corrected. 

 But it is when we come to finer subdivisions, and have to dis- 

 entangle the ultimate twigs of the tree of life, that the difficulties 

 become almost insuperable, and if we are to attempt it, it behoves 

 us to work according to the most accurate and methodical system 

 we can devise. 



Now in all sorting-out processes it is obvious that we must fix 

 upon a unit. We must then select these units and lay them 

 together in groups, and these groups again into groups of a higher 

 order, and so on. Hence the first question which confronts us is, 

 What unit shall we adopt for our attempts to classify the organic 

 world? The case is of course a specially difficult one because the 

 variations are so multitudinous, and of so many different degrees 

 of value, vast numbers being excessively minute. But the more 

 difficult it is the more perfect our technique must be. The very 

 first step we can take towards this perfection of our technique 

 is to see that our units have some actual demonstrable existence, 

 and the next that they can be fairly accurately defined. Unless 

 these conditions are fulfilled one would fancy that all our 

 attempts at sorting were but waste labour. 



Now with this insight into the needs of the case it is not 

 difficult to see why the Linnean system, however excellent it may 

 be as a formula for a natural classification when we have worked 

 such a classification out, is useless as a technique for the work 

 itself. Its unit is no longer even approximately definable, it is 

 in fact one of the very divisions which we wish to discover, and of 

 all the divisions that one which is the most difficult to discover. 

 I refer to the ideal genetic group called 'species,' which is the 

 unit of classification under our present system. Borrowed at first 

 as the fixed created species of the theologian and of common 

 observation, these species have served as the most natural units 

 to be marshalled into genera and so on. It is true that varieties 

 early came in as difficulties, so slight however as to be negligible. 

 So long as we believed in fixed species, they could be regarded as 

 accidental appendages of one kind or another which did not 

 affect the existence of the unit. The species was the funda- 

 mental fact. 



It is not uninteresting to enquire why, so long after we all 

 recognise that there is no such thing as a fixed species, and that 

 all is in a state of flux, we have not altered our unit. I explain 

 this as due to the fact that universal variability has been regarded 

 too theoretically. In practice it may be argued we see only what 

 our fathers saw, that is, fixed species. In practice, therefore, there 



