VARIATION UNDER NATURE 93 



species, are altogether excluded from the tables. These 

 facts are of plain signification on the view that species 

 are only strongly-marked and permanent varieties; for 

 wherever many species of the same genus have been 

 formed, or where, if we may use the expression, the 

 manufactory of species has been active, we ought gen- 

 erally to find the manufactory still in action, more espe- 

 cially as we have every reason to believe the process of 

 manufacturing new species to be a slow one. And this 

 certainly holds true, if varieties be looked at as incipient 

 species; for my tables clearly show as a general rule that, 

 wherever many species of a genus have been formed, the 

 species of that genus present a number of varieties, that 

 is of incipient species, beyond the average. It is not 

 that all large genera are now varying much, and are 

 thus increasing in the number of their species, or that 

 no small genera are now varying and increasing; for if 

 this had been so, it would have been fatal to my theory; 

 inasmuch as geology plainly tells us that small genera 

 have in the lapse of time often increased greatly in size; 

 and that large genera have often come to their maxima, 

 decline, and disappeared. All that we want to show is 

 that, where many species of a genus have been formed, 

 on an average many are still forming; and this certainly 

 holds good. 



Many of the /Species included ivithin the Larger Genera re- 

 semble Varieties in being very closely^ but unequally^ 

 related to each other ^ and in having restricted ranges 



There are other relations between the species of large 

 genera and their recorded varieties which deserve notice. 

 We have seen that there is no infallible criterion by 



