96 Bird - Lore The great majority of them are no more than collectors ; some are describers, but very few are those that try to explain. The incentives with most of them are, the esthetic one, — to hoard objects beautiful in color and form ; and the huntsman's instinct, — to seek what is difficult to discover. This aspect of collecting is like that of the bibliophile, who seeks beautiful bindings, rare editions, first imprints, but never reads his books ; or like that of the collector of china and pottery, or of postage stamps. Are not the pages of the catalogues of the dealers in birds' eggs full of advertisements of postage stamps and curios ? These dealers understand their public. Oolo- gists may be painfully exact in keeping notes of their specimens, but have an abhorrence for an egg-shell punctured at both ends, because this spoils its beauty for them. They have just the same delight in an abnormal speci- men as a bibliophile in a unique print with the title-page omitted. This form of oology can be justified on the esthetic side; but it is no more than a pleasurable hobby, is in no manner scientific, and its licenses should rather read "for esthetic purposes." Such men are seeking beauti- ful oddities, with the instinct of a jeweler, but do not enlighten the world in any degree. Let us ask what interpretative value might be derived from the study of blown egg-shells ? They present characters of size and form, of color, number, sculpturation, thickness and consistency. Qualities such as these any broad taxonomist immediately recognizes as of trivial value, because minimally conservative and therefore of small use in tracing genetic affini- ties of the birds producing the eggs. Only one comprehensive work is known to me, — that of Des Murs, which attempts to base racial connections of birds upon the characters of their egg-shells. An examination of his con- clusions shows how full they are of exceptions, though undoubtedly his work deserves more consideration than it has generally received. A later paper by Shufeldt states a number of supposed laws in regard to form and coloration, but none of these hold for all cases, and one turns from its perusal with a doubt as to the ultimate value of such study. Newton has pointed out in his ' Dictionary of Birds ' that the study of egg-shells prom- ises few interpretations of any broad significance. The number of eggs in a set is, to some extent at least, dependent upon the relative size of the eggs; the explanation of the size cannot be obtained by any investigation of egg- shells, but must be founded upon the phenomena within the ovary. The number of sets, also, cannot be elucidated from any study of the egg-shells; it is probably rather a function of the environmental condition of the length of the annual period favorable for brooding. The form of the egg must be ex- plained from a knowledge of the shape of the oviduct and cloaca. The degree of roughness of a shell's surface is dependent, so far as we know, upon the consistency of the calcareous secretion, and that, as well as its thickness, upon the nature of the genital organs. Not one of these charac- ters can be explained by a knowledge of egg-shells alone.
