Australian ewes know the bleat of their own lambs, however immense the flock, and all through nature we find this useful note of recognition. One of the most philosophic interpreters of living phenomena, viewing things from a very recent standpoint--Professor J. Arthur Thomson, in his fascinating _Biology of the Seasons_ (p. 174), writing of the colour and texture of birds’ eggs, says:-- “In some cases, it is said, the shell registers hybridism--a very remarkable fact. It is another illustration of the great, though still vague, truth that the living creature is a unity through and through, specific even in the structure of the egg-shell within which it is developed. For although the shell is secreted by the walls of the oviduct, it seems to be in some measure controlled by the life of the giant-cell--the ovum--within.” Such pattern-forming qualities are found in many fields of nature, very beautifully, for example, as we have seen, in the skin of the zebra; on the back of a mackerel; in the grain of various kinds of wood; in the veining of leaves and petals; and in the covering or substance of seeds such as the nutmeg and scarlet runner bean. Sir Charles Lyell, in his _Elements of Geology_, figures the ribbing of sand on the sea-shore in a wood-cut which might be an enlarged diagram of human skin. (See fig. on page 32). In his _Principles of Geology_ (5th ed., vol. i., p. 323) there is, again, a figure described as a section of “spheroidal concretionary Travertine,” which contains many linings strikingly like those with which we have to deal in this little work. [Illustration: _a_. section of pine-wood stem. _b_. a human thumb-print.] It follows from these analogies that a method of analysing and classifying such patterns might have very wide utilities beyond its relation to finger-prints. It is easy, for example, to recognize the same zebra in quite different pictures. Another point of practical importance is this, that a smudgy or blotchy impression, supposed to be that of a criminal present at some seat of crime, might be the impressed copy merely of some object or texture other than human skin, but containing lineations of similar arrangement. An outworn transversely cut branch of a tree might readily produce a print like that of a human finger. An expert would probably notice that in the lineations there were no real junctions, each woody ring remaining apart from the others; but, again, there are some human fingers of such patterns. I think the bloody smear officially reproduced as impressed on a post-card in facsimile, and purporting to have come from “Jack the Ripper,” at the time of the Whitechapel horrors in the eighties, may have been produced by the sleeve of a twilled coat smeared with blood. It contained no characters specially characteristic of skin lineations, which it was presumed to be an example of, as impressed.