ARTIFICIAL DEVICES 25 



If all the races (so-called species) belonging to a kingdom of living 

 bodies were thoroughly known, as well as their true affinities, so that 

 the sorting out of these races and their allocation in various groups 

 were in conformity with their natural affinities, the classes, orders, 

 sections and genera would be families of different sizes, for all these 

 divisions would be larger or smaller parts of the natural order. 



On such an assumption, nothing doubtless would be more difficult 

 than to assign the boundaries between these different divisions ; 

 arbitrary opinion would produce incessant variation, and there would 

 be no agreement except where gaps in the series made clear demarca- 

 tions. 



Fortunately for the practicability of the artifice which we have to 

 introduce into our classifications, there are many races of animals 

 and plants that are still unknown to us, and will probably remain so, 

 since insuperable obstacles are placed in our way by the places where 

 they Uve and other circumstances. The gaps thence arising in the 

 series, whether of animals or plants, will leave us for a long time still, 

 and perhaps for ever, the means of setting up the majority of the 

 divisions. 



Custom and indeed necessity require that a special name should 

 be given to each family and to each genus so as to be applicable to 

 the objects it contains. It follows that alterations in the boundaries, 

 extent and determination of families will always cause a change in 

 their nomenclature. 



Genera. — The name of genus is given to combinations of races or 

 so-called species that have been united on account of their affinities, 

 and constitute a number of small series marked out by characters 

 arbitrarily selected for the purpose. 



When a genus is well made, all the races or species comprised in it 

 resemble one another in their most essential and numerous characters. 

 They differ only among themselves in characters less important, 

 but sufficient to distinguish them. 



Well made genera are thus really small families, that is to say, real 

 parts of the actual order of nature. 



Now we have seen that the series to which we give the name of 

 family are liable to vary as to their boundaries and extent, according 

 to the opinions of authors who arbitrarily change their guiding 

 principles. In the same way the boundaries of genera are exposed 

 to infinite variation because different authors change at will the 

 characters employed to determine them. Now a special name has to 

 be assigned to each genus ; and every change in the constitution 

 of a genus involves nearly always a change of name. It is difficult 

 therefore to exaggerate the injury done to natural science by 



