92 THE ORIGIN OF SPECIES 



there is no close relation to the size of the genera. The 

 cause of lowly-organized plants ranging widely will be 

 discussed in our chapter on Geographical Distribution. 



P'rom looking at species as only strongly-marked and 

 well-defined varieties, I was led to anticipate that the spe- 

 cies of the larger genera in each country would oftener 

 present varieties than the species of the smaller genera; 

 for wherever many closely related species {i.e., species 

 of the same genus) have been formed, many varieties or 

 incipient species ought, as a general rule, to be now form- 

 ing. Where many large trees grow, we expect to find 

 saplings. "Where many species of a genus have been 

 formed through variation, circumstances have been favor- 

 able for variation; and hence we might expect that 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 plants of twelve countries, and the coleopterous in- 

 sects of two 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. More- 

 over, 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 



