CnAP. 11. SPECIES OF LARGER GENERA VARIABLE. 65 



than the species of the smaller g'enera ; for wherever many 

 closely-related species (i. e., species of the same genus) have 

 been fornietl, many varieties or incipient species ought, as a 

 general rule, to be now forming. Where many large trees 

 grow, we expect to find saplings. Where many species of a 

 genus have been formed tkrough variation, circumstances have 

 been favorable for variation ; and hence we might expect thai 

 the circumstances would generally be still favorable to varia- 

 tion. 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 

 j^lants of twelve countries, and the coleopterous insects of two 

 districts, into two nearly equal masses, the species of the 

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

 the other sid(?, and it has invariably proved to be the case that 

 a larger proportion of ±he 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 pre- 

 sent any varieties, invariably present a larger average number 

 of varieties than do the species of the small genera. Both these 

 results follow when another diWsion is made, and when all the 

 least genera, with from only one to four species, are absolutely 

 excluded from the tables. These facts are of plain significa- 

 tion 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 expres- 

 sion, the manufactory of species has been active, we ought 

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

 cially as we have every reason to believe the process of manu- 

 facluring new species to be a slow one. And this certainly 

 is the case, if varieties be looked at as incipient species ; for 

 my tables clearly show as a general rule that, wherever many 

 speci(^s of a genus have been formed, the species of that genus 

 present a nvunber of varieties, that is, of incipient species, be- 

 yond the average. It is not that all large genera are now 

 varying nuich, and are thus increasing in the lunnber of their 

 species, or that no small genera are now varying and increas- 

 ing; for if this had l)een 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, declined, 



