]iv INTRODUCTION 



families, orders and classes from one another. This is 

 what Lamarck calls classification. Since the series represents 

 an even and regular progress in complexity of organisation, 

 the selection of the points on the scale where our lines of 

 demarcation shall be drawn is purely arbitrary : such divisions 

 have no objective reality. Thus classification, as Lamarck 

 conceived it, is not a science, but an art : it involves a 

 question not of truth or error, but merely of convenience. 

 Distribution, on the other hand, is a genuine science, not 

 dependant on our convenience : our attempts at distribu- 

 tion are either true or false : if true, they correspond to 

 an order which has actual objective existence. 



The word " classification " in modern biology does not 

 exactly correspond to either of these two terms. We no 

 longer believe in a linear series of animals : on the other 

 hand, the groupings and divisions which we make among 

 animals are not regarded as subjective conveniences, but as 

 objective realities. The entire collection of living animals 

 is broken up into discontinuous groups : and the gaps 

 between these groups are not gaps in our minds, but gaps 

 in external nature. Hence, modern classification is a true 

 science. To this extent it resembles Lamarck's distribution 

 and differs from his classification. I have allowed myself a 

 certain degree of latitude in deciding when either of these 

 words is to be translated by the English " classification," 

 a word that inevitably carries with it to modern readers all 

 its modern biological connotations. 



It remains only to indicate the services which Lamarck 

 rendered to classification ; and they were undoubtedly very 

 great. It was certainly unfortunate that he should have 

 adopted the conception of a linear series. He not only adopts 

 it, but most energetically defends it : 



" Man is condemned to exhaust all possible errors when 

 he examines any set of facts, before he recognises the truth. 

 Thus it has been denied that [animals] can really be arranged 

 in a true series according to their affinities. . . . Several 

 naturalists have imagined that the affinities among animals 



