CHAPTER VIII 



THE ORGANIC AND THE INORGANIC 



IT is convenient that we should express the results of 

 biological investigation in schemes of classification, for 

 only in this way can we reduce the apparent chaos 

 of naturally occurring organic things to order, and 

 state our knowledge in such a way that it can easily 

 be communicated to others. But we must always 

 remember that the classifications of systematic bio- 

 logy are conceptual arrangements, depending for their 

 precise nature on the point of view taken by their 

 authors. The clear-cut distinctions that apparently 

 separate phylum from phylum, class from class, order 

 from order, and so on, do not really exist. There are 

 no such categories of organisms in nature as genera, 

 families, and the higher groupings. All that we can 

 say exist naturally are the species, since all the organ- 

 isms composing each of these groups are related to- 

 gether by ties of blood-relationship, and all are isolated 

 from the organisms composing other species by physio- 

 logical dissimilarities which render the plants or animals 

 of one species infertile with those of any other. Such 

 would doubtless have been the opinion of most botanists 

 and zoologists prior to the work of de Vries, but we 

 must now recognise that the systematic, or Linnean, 

 species of the nineteenth century was just as artificial 

 a category as were the genera and families. Our 

 arrangements of plants and animals into systematic 



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