"Elsewhere (_Origin of Species_, p. 158) Mr. Darwin points out that modifications which appear to present obvious utility are often found on further examination to be really useless. This latter consideration, therefore, may be said to act as a foil to the one against which I am arguing, namely, that modifications which appear to be useless may nevertheless be useful. But here is a still more suggestive consideration, also derived from Mr. Darwin's writings. Among our domesticated productions changes of structure--or even structures wholly new--not unfrequently arise, which are in every way analogous to the apparently useless distinctions between wild species. Take, for example, the following most instructive case:-- [Illustration: Fig. 2.--Old Irish Pig, showing jaw-appendages (after Richardson).] "'Another curious anomaly is offered by the appendages described by M. Eudes-Deslongchamps as often characterizing the Normandy pigs. These appendages are always attached to the same spot, to the corners of the jaws; they are cylindrical, about three inches in length, covered with bristles, and with a pencil of bristles rising out of a sinus on one side; they have a cartilaginous centre with two small longitudinal muscles; they occur either symmetrically on both sides of the face, or on one side alone. Richardson figures them on the gaunt old Irish Greyhound pig; and Nathusius states that they occasionally appear in all the long-eared races, but are not strictly inherited, for they occur or fail in the animals of the same litter. As no wild pigs are known to have analogous appendages, we have at present no reason to suppose that their appearance is due to reversion; and if this be so, we are forced to admit that a somewhat complex, though apparently useless, structure may be suddenly developed without the aid of selection[97].'" [97] _Variation_, &c. vol. i. pp. 78-79. To this case Mr. Wallace objects:-- "But it is expressly stated that they are not constant; they appear 'frequently' or 'occasionally,' they are 'not strictly inherited, for they occur or fail in animals of the same litter'; and they are not always symmetrical, sometimes appearing on one side of the face alone. Now, whatever may be the cause or explanation of these anomalous appendages, they cannot be classed with 'specific characters,' the most essential features of which are, that they _are_ symmetrical, that they _are_ inherited, and that they _are_ constant[98]." [98] _Darwinism_, pp. 139-40. But, to begin with, I have not classed these appendages with "specific characters," nor maintained that Normandy pigs ought to be regarded as specifically distinct on account of them. What I said was:--