72 ORIGIN OF SPECIES 



hence we might expect that the circumstances would gener- 

 ally be still favourable to variation. On the other hand, if 

 we look at each species as a special act of creation, there is 

 no apparent reason why more varieties should occur in a 

 group having many species, than in one having few. 



To test the truth of this anticipation I have arranged the 

 plants of twelve countries, and the coleopterous insects of 

 tVi'O districts, into two nearly equal masses, the species of 

 the larger genera on one side, and those of the smaller genera 

 on the other side, and it has invariably proved to be the case 

 that a larger proportion of the species on the side of the 

 larger genera presented varieties, than on the side of the 

 smaller genera. Moreover, the species of the large genera 

 which present any varieties, invariably present a larger 

 average number of varieties than do the species of the small 

 genera. Both these results follow when another division is 

 made, and when all the least genera, with from only one to 

 four 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 generally to find the manufactory 

 still in action, more especially 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: inas- 

 much 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. 



