Origin of Species Variorum

it, antenna. The antenna being touched causes a certain membrane to rupture through its own irritability, and this sets free a spring by which the pollen-mass is shot forth, like an arrow, in the right direction, and adheres by its viscid extremity to the back of the bee. The pollen-mass is thus carried to another flower, where it is brought into contact with the stigma, which is viscid enough to break certain elastic threads, and to retain the pollen-mass, which then performs its office of fertilisation.

How, it may be asked, in the foregoing and in innumerable other and similar cases, can we understand the cause of such a wide scale of complexity and of such multifarious means for gaining the same end, both in the case of forms widely remote from each other in affinity, and with forms so closely allied as are the two orchids last described? ↑ It was shown, when we discussed the air-breathing apparatus of certain crustaceans, that the process of adaptation for any purpose may start from two or more forms already differing from each other to a considerable degree, and that in almost all cases the nature of the variability, on which natural selection has to work, will be different; consequently, the final structure gained through natural selection, though serving for the same purpose, will be different. We must also bear in mind that every well-developed organism has already passed through a long course of modification; and that each modified structure tends to be inherited, so that it will not readily be lost, but may be modified again and again. Hence the structure of each part of each species, for whatever purpose used, will be the sum of the many inherited changes, through which that species has passed during its successive adaptations to changed habits and conditions of life.

Finally then, although in many cases it is most difficult to