284 RECAPITULATION. [Chap. XV. 



against an enemy, causing the bee's own death; at 

 drones being 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 ichneumonidse feeding within 

 the living 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 production 

 of distinct species. In both cases physical conditions 

 seem to have produced some direct and definite effect, 

 but how much we cannot say. Thus, when varieties 

 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 

 plaved an important part, so that when one part has 

 been modified other parts have been necessarily modified. 

 With both varieties and species, reversions to long-lost 

 characters occasionally occur. How inexplicable on the 



