Origin of Species Variorum

Comparison with 1869

supported on a style; but in some Compositæ, the male florets, which of course cannot be fecundated, have a rudimentary pistil, for it is not crowned with a stigma; but the style remains well developed, and is clothed with hairs, in the usual manner, for brushing the pollen out of the surrounding and conjoined anthers. Again, an organ may become rudimentary for its proper purpose, and be used for a distinct object: in certain fish the swimbladder seems to be nearly rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung. Other similar instances could be given.

Organs, however little developed, if of use, should not be called rudimentary; they cannot properly be said to be in an atrophied condition; they may be called nascent, and may hereafter be developed to any extent by natural selection. Rudimentary organs, on the other hand, are essentially useless, as teeth which never cut through the gums. ↑ As they would be of even less use, when in a still less developed condition, they cannot have been formed through variation and natural selection, which latter acts solely by the preservation of useful modifications. They relate to a former state of things, and have been partially retained by the power of inheritance. It is difficult to know what are nascent organs; looking to the future, we cannot of course tell how any part will be developed, and whether it is now nascent; looking to the past, creatures with an organ in a nascent condition will generally have been supplanted and exterminated by their successors with the organ in a more perfect and developed condition. The wing of the penguin is of high service, and acts as a fin; it may, therefore, represent the nascent state of the wings of birds; not that I believe this to be the case, it is more probably a reduced organ, modified for a new function: the wing of the Apteryx is useless, and is truly rudimentary. The simple filamentary limbs of the Lepidosiren apparently are in a nascent state; for, as Owen has remarked, they are the "beginnings of organs which attain full functional development in higher vertebrates." The mammary glands of the Ornithorhynchus may, perhaps, be considered, in comparison with the udder of a cow, as in a nascent state. The ovigerous frena of certain cirripedes, which are only slightly developed and which have ceased to give attachment to the ova, are nascent branchiæ. Rudimentary organs in the individuals of the same species are very liable to vary in degree of development and in other respects. Moreover, in closely allied species, the degree to which the same organ has been rendered rudimentary occasionally differs much. This latter fact is well exemplified in the state of the wings in female moths in certain groups. Rudimentary organs may be utterly aborted; and this implies, that in certain animals or plants, parts are entirely absent which analogy would lead us to expect to find, and which are occasionally found in monstrous individuals. .. .. .. Thus in most of the Scrophulariaceæ the fifth stamen is utterly aborted; yet we may conclude that a fifth stamen once existed, for a rudiment of it is found in many species of the family, and this rudiment occasionally becomes perfectly developed, as may be seen in the common snap-dragon. In tracing the homologies of any part in different members of the same class, nothing is more common, or more necessary, in order fully to understand the relations of the parts, than the discovery of rudiments. This is well shown in the drawings given by Owen of the bones of the leg of the horse, ox, and rhinoceros.

It is an important fact that rudimentary organs, such as teeth in the upper jaws of whales and ruminants, can often be detected in the embryo, but afterwards wholly disappear. It is also, I believe, a universal

supported on the style; but in some Compositæ, the male florets, which of course cannot be fecundated, have a pistil, which is in a rudimentary state, for it is not crowned with a stigma; but the style remains well developed, and is clothed with hairs as in other compositæ, for the purpose of brushing the pollen out of the surrounding anthers. Again, an organ may become rudimentary for its proper purpose, and be used for a distinct object: in certain fish the swim-bladder seems to be rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung. Other similar instances could be given. ↑

Rudimentary organs in the individuals of the same species are very liable to vary in degree of development and in other respects. Moreover, in closely allied species, the degree to which the same organ has been rendered rudimentary occasionally differs much. This latter fact is well exemplified in the state of the wings of the female moths in certain groups. Rudimentary organs may be utterly aborted; and this implies, that we find in an animal or plant no trace of an organ, which analogy would lead us to expect to find, and which is occasionally found in monstrous individuals of the species. Thus in the snapdragon (antirrhinum) we generally do not find a rudiment of a fifth stamen; but this may sometimes be seen. In tracing the homologies of the same part in different members of a class, nothing is more common, or more necessary, than the use and discovery of rudiments. This is well shown in the drawings given by Owen of the bones of the leg of the horse, ox, and rhinoceros.