Heredity in Abnormal-Toed Cats

Abstract

THE calculation made by Mr. J. H. Hodd in last week's NATURE (p. 53) of the numerical proportion of the sexes of Mr. Poulton's race of extra-toed cats, in relation to the recurrence of the abnormity, is very interesting as an inferrable deduction from the premises of Mr. Poulton's elaborate tabulation of his observations; but it is, I think, doubtful whether it is not misleading as a generalisation from the facts collected by him. A conclusion arrived at by means of a mathematical method is too absolute an inference, and not necessarily reliable, when applied to purely biological cases, on account of the numerous intervening factors (perhaps mostly unknown, but yet of importance) which are incapable of being appreciated within such an estimate, and which may, in consequence, invalidate the main point under consideration. This appears to be the case on the present occasion; for Mr. Poulton mentions, in describing the kittens of VIII⁵ (p. 39), that by far the most highly specialised development of the abnormity he has observed, throughout the entire race, was attained in a male—VIII⁵. Considering that the large majority of individuals possessing the character are of the sex, as pointed out by Mr. Hodd, this fact is really very striking. But, at the same time, if the point alluded to by Mr. Hodd were considered as amounting to a principle, we should naturally be led to infer that, the abnormity might become equivalent to a secondary sexual character, which is so improbable that it scarcely bears suggestion. Besides, it is necessary to bear in mind that all the observations carried on as yet by Mr. Poulton have dealt with the ♀ influence alone; and it may be accounted for by the very reason that all the ♂s have been carefully eliminated from exercising any influence on the race, that the predominant effect, numerically, is on the ♀ side; while it is most probable that if an abnormal ♂ were selected (say, the individual just referred to) as a starting-point for experiment with normal ♀s, the result would exhibit a general tendency towards superior persistence of the character operating with greater potency amongst the males than the females. It would be very interesting to experiment in this manner under the isolation happily promised in the Madeiran Islands.