134 TEST CASES [ch. xii 



more than of medium or large (cf. p. 98). In places where there 

 are many of them close together, as with the big genera Eugenia 

 or Memecylon in Ceylon, they are all more or less closely related, 

 though many of them are quite good Linnean species. Attention 

 may also be drawn to the "Jordanian" species in big genera like 

 Draba or Hieracium. 



4. The varying species are relatively most numerous in those 

 classes, orders, and genera which are the simplest in structure. 



5. As with species, so with genera and families. . .upon the 

 whole those are the best limited which consist of plants of complex 

 floral structure. 



6. Those classes and families which are the least complex in 

 organisation are the most widely distributed, that is to say that they 

 contain a larger proportion of widely dispersed sjjecies. 



7. This tendency of the least complex species to be most widely 

 diffused is most marked in Acotyledons (Cryptogams) and least so 

 in Dicotyledons. 



8. The ynost widely distributed and commonest species are the 

 least modified. 



All these latter axioms go together, and obviously fit exactly 

 with what would be expected under the law of age and area, 

 which makes the older (and therefore on the whole the simpler) 

 forms to occupy more area than the younger and more complex. 

 The fact that all these dicta are axiomatic does not say much for 

 the supposed continual improvement in adaptation under the 

 operations of natural selection, especially as this theory also tries 

 to explain greater range by the same improved adaptation. The 

 whole of the axioms are rather against the Darwinian theory of 

 progress, and are in much better accord with that of differen- 

 tiation. 



TEST CASE XX. THE POSITION OF THE LARGEST 



GENERA IN A FAMILY 



On the theory of natural selection, one can make no prediction 

 whatever as to the position in the classification of a family of 

 the largest genera in it. There seems no reason whatever in any- 

 thing that we know about them which should show that they 

 should be near together, or that they should be far apart. But 

 upon the theories of diff'erentiation and age and area, the largest 

 genera should on the whole be the most widely separated, in- 



