OF NATURAL SELECTION. 373 



in the same nest, but in some few alone; and that by the 

 survival of the communities with females which produced 

 most neuters having the advantageous modification, all 

 the neuters ultimately came to be thus characterized. Ac- 

 cording to this view we ought occasionally to find in the 

 same nest neuter insects, presenting gradations of struct- 

 ure; and this we do find, even not rarely, considering how 

 few neuter insects out of Europe have been carefully ex- 

 amined. Mr. F. Smith has shown that the neuters of 

 several British ants difEei- surprisingly from each other in 

 size and sometimes in color; and that the extreme forms can 

 be linked together by individuals taken out of the same nest: 

 I have myself compared perfect gradations of this kind. 

 It sometimes happens that the larger or the smaller sized 

 workers are the most numerous; or that both large and 

 small are numerous, while those of an intermediate size 

 are scanty in numbers. Formica flava has larger and 

 smaller workers, with some few of intermediate size; and, 

 in this, species, as Mr. F. Smith has observed, the larger 

 workers have simple eyes (ocelli), which, though small, can 

 be plainly distinguished, whereas the smaller workers have 

 their ocelli rudimentary. Having carefully dissected 

 several specimens of these workers, I can affirm that the 

 eyes are far more rudimentary in the smaller workers than 

 can be accounted for merely by their proportionately lesser 

 size; and I fully believe, though I dare not assert so posi- 

 tively, that the workers of intermediate size have their 

 ocelli in an exactly intermediate condition. So that here 

 we have two bodies of sterile workers in the same nest, dif- 

 fering not only in size, but in their organs of vision, yet 

 connected by some few members in an intermediate 

 condition. I may digress by adding, that if the smaller 

 workers had been the most useful to the community, and 

 those males and females had been continually selected, 

 which produced more and more of the smaller workers, 

 until all the workers were in this condition, we should 

 then have had a species of ant with neuters in nearly the 

 same condition as those of Myrmica. For the workers of 

 Myrmicahave not even rudiments of ocelli, though the male 

 and female ants of this genus have well-developed ocelli. 



I may give one other case: so confidently did I expect 

 occasionally to find gradations of important structures 



