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July, 1914 A PLEA FOR COMPARATIVE OOLOGY 163 or teapots; also, that such information should be as complete and accurate as possible. With the information or "knowledge" so available the intelligent col- lector will proceed to methodically formulate and arrange it in a rational system, and when he has done so he is perfectly justified in claiming scientific results, so far as they go. The point too often overlooked is that isolated observations are of little value: they must be correlated. If we attempt to apply some process of investigation to a "faunal" collec- tion the weakness of the latter becomes at once apparent. To make this clearer let us consider a complete but restricted one like that from the District of Columbia. We will find that it contains two species of falcons' eggs, F. spar- verius and F. p. anatum. The eggs of the Duck Hawk are much larger and darker than those of the Sparrow Hawk, but there is a certain likeness in the type of markings; is this a general characteristic of all falcon's eggs or a pecu- liarity shared by a few ? We must go farther afield to answer this query. I find in my cabinets the eggs of more than a score of falcons: F. mexicanus and phaloena from California, fusco-coerulescens from Texas, columbarius from As- sinaboia, paulus from Florida, subbuteo, anatum, tinnunculus and aesalon from the British Isles, vespertinus from Hungary, eleonorae from Greece, sacer from Russia, cenchris from Asia Minor, obscurus from Siberia, and so on through japonicus to the distant shores of the Pacific. In latitude there is likewise a wide distribution as shown by rusticolus and gyrfalco from Lapland and Ice- land, cenchroides, unicolor and others from Australia, and finally, rupicola and rupicoloides from South Africa. The genus is practically cosmopolitan, the various species nest in almost every possible situation (except under ground), a series of eggs presents a wonderful diversity in color and marking, yet all are distinctly true to one type: each one could be picked out as a falcon's egg and, so far as I am aware, could be mistaken for none other. (Eggs of the Honey Buzzards, Per.n]s, and certain Polyborine species--for example Milvago chimango--seem to approach them most closely.) I think it will be evident that such information is both interesting and de- sizable, but for its demonstration a collection must be formed along rather de- finite lines, based on the natural relations of birds rather than on their geo- graphical distribution. Such a "group" collection need not, of course, be uni- versal in scope, but should embrace as many genera, families or orders as the collector 's means and opportunities permit, the main point being to make it as complete and accurate as practicable within its natural limitations. Of course a general collection of this sort presents many difficulties and, for most of us, would entail prohibitive expense. Hence, I would by no means advise every collector to lightly go in for exotic material of all sorts--and I speak from many years' experience--nor is this essential. A faunal collection may be am- plified in special directions, and this is being done already to some extent. Thus the Mniotiltidae have long been favorites with American collectors. In Europe this is more common, and I know one colletgot who has a marvellous array of eggs of the Tubinares and Lariformes, and another who specializes in the Fringillidae while endeavoring to complete a faunal collection of the Brit- ';sh Isles. But the faunal idea seems to be an obsession with many collectors, and they carry it to the absurd degree of separating entirely their American and "'foreign" material. It would be quite as logical to arrange our Bald Eagles' eggs so that thos? of the Alaskan form are placed in the top drawer, along with