Dr. Berry Hart quotes from the records of another observer (Wilder) in which there was a pair of “identical” twins, in whom the similarity was complete even to the finger-prints. [_Brit. Med. Jour._, July 29th, 1911, p. 215.] I have found in the same family male and female with _resembling_ finger-prints, but none which could be called identical, but opportunities of comparing twins of the same sex do not often occur. While writing this chapter I examined twins of the same sex (female). Their finger-prints are very similar, but details diverge in many directions. The matter merits close attention. But how are we to determine that twins of the same sex are from one ovum, seeing that there might be a coincidence of twins of the same sex proceeding from separate ova? If their finger-prints are “identical,” is that the main evidence? or do identity of features, colour of hair, voice, manners, and character, come up independently? If one questions the theory, the “identity” must be very complete indeed, to give it vraisemblance, for how often do we not find that children of the same parents, not twins, but born with many years intervening, show most striking resemblance? The alleged complete identity of finger-patterns, however, is a most interesting and novel point, and ought to receive close attention from parents and physicians. A curious fact about hereditary resemblance is this, which I have frequently observed. A child resembles, say, a mother as a rule, but at some emotional, angry, or vexed moment, lines are marked in the face by muscular movements which bring out like a mask a striking likeness, say, of the father, or of some other progenitor. Besides this, a child at different stages may resemble in succession different near relatives, and in a very striking degree resemble them. But with regard to finger-patterns there is no such variability. Even a month or two before a child is born its little heraldic crest begins to be firmly fixed for each finger, as it is to be throughout life. The disease called Acromegaly, or giant growth, involves great expansion of the ridges and furrows, but no case of actual change of patterns has been observed as yet. The attention of medical men should be given to this affection in regard to modification of linear arrangement. The likeness or divergence of finger-patterns in neighbouring supernumerary fingers and toes might yield interesting results if carefully recorded. Extra fingers are commoner than extra toes. The webbing of fingers, as in the chimpanzee, might also be noticed, and any association with retrograde patterns, in the fingers concerned.