284 RECAPITULATION. [Chap. XV. 



an enemy, causing the bee's own death; at drones be^ 

 ing produced in such great numbers for one single act, 

 and being then slaughtered by their sterile sisters; at 

 the astonishing waste of pollen by our fir-trees; at the 

 instinctive hatred of the queen-bee for her own fertile 

 daughters; at the ichneumonida feeding within the liv- 

 ing bodies of caterpillars; or at other such cases. The 

 wonder indeed is, on the theory of natural selection, 

 that more cases of the want of absolute perfection have 

 not been detected. 



The complex and little known laws governing the 

 production of varieties are the same, as far as we can 

 judge, with the laws which have governed the produc- 

 tion of distinct species. In both cases physical condi- 

 tions seem to have produced some direct and definite 

 effect, but how much we cannot say. Thus, when varie- 

 ties enter any new station, they occasionally assume some 

 of the characters proper to the species of that station. 

 With both varieties and species, use and disuse seem to 

 have produced a considerable effect; for it is impossible 

 to resist this conclusion when we look, for instance, at 

 the logger-headed duck, which has wings incapable of 

 flight, in nearly the same condition as in the domestic 

 duck; or when we look at the burrowing tucu-tucu, 

 which is occasionally blind, and then at certain moles, 

 which are habitually blind and have their eyes covered 

 with skin; or when we look at the blind animals in- 

 habiting the dark caves of America and Europe. With 

 varieties and species, correlated variation seems to have 

 played an important part, so that when one part has 

 been modified other parts have been necessarily modi- 

 fied. With both varieties and species, reversions to long- 

 lost characters occasionally occur. How inexplicable on 



