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164 THE CONDOR Vol. XVI the ducks and auklets, while specimens from Florida would be located at the bottom, congenially surrounded by spoonbills and limpkins! To my way of thinking the oologist who, with a given amount of time (and money) starts out to illustrate all that is ascertainable about the nidification of, say, our North American Icteridae, can accomplish far more in the way of scientific results than by attempting to accumulate a "set" of every known form on the A. 0. U. List. While the number of problems open to investigation by the intensive study of a group collection is almost endless, the inviting road towards broad generalizations is far less easy than it seems ;' for on every hand there is abund- ant opportunity for false and hasty conclusions which will inevitably carry us far afield. Hence, the systematists are prone to complain that we can afford them little assistance in their labors, as likeness or dissimilarity in birds' eggs cannot generally be relied upon to indicate a corresponding degree of relation- ship among the birds themselves. Let us cheerfully admit it, proceed to show where the correspondence begins and ceases and then, if possible, ascertain why. But in many cases the correspondence is really very close; such exam- pies as those of the owls, tinamous and shore-birds will occur to all, and it is said that the relationship of this last group to the gulls and terns was first pointed out by oologists. Even small groups are sometimes sharply defined, such as the peculiar markings characteristic, I believe, of the genus Myiarchus. On the other hand, the many exceptions, while difficult and confusing, are no less interesting and would doubtless prove equally informing if we held the explanatory key. Thus, eggs of the herons are greenish, while those of the slightly differentiated bitterns may be nearly vehite or decidedly brown, but 'are still unspotted. Among their allies, the ibises and spoonbills, however, variation runs riot and we find plain white (e.g., Ibis toolucca), light greens, (lark greens and spotted types in great diversity. Such examples become par- ticularly puzzling when we observe that certain species, even more closely al- lied, occupying the same restricted habitat, and having identical methods of nidificaton, may yet produce eggs extremely unlike; as an American example compare the whitish, spotted eggs of Toxostoma benditel with the plain, green- ish specimens of its neighbor, T. crissalis. It is particularly in the investigation of such facts that the group collec- tion, of restricted scope, should be of value. Suggestive facts may be forth- coming; thus, if we consider the eggs of the Miraidac as a .whole we find that while nearly all are commonly spotted, those that are plain (e.g., T. crissali?, G. carolinesis) seem to always adhere to that type, while in the other forms there is an occasional tendency to lightly marked or unmarked examples. Let us contrast this ?vith an illustration from the genus Accipiter; eggs of fuscus and nisus are, typically, richly marked, those of cooperi are commonly plain, while specimens of cirrhocephalus (Australian) in my collection are intermedi- ate. But I have one set of cooperi (taken by Bingaman) which shows about as much superficial coloring as average specimens of B. borealis, while eggs with a few faint spots are not uncommon. Apparently in the g9nus Accipiter either the habit of laying plain eggs has not yet become fixed in any species, as it has with some Miraidac, or, more probably, I think, the habit of laying colored eggs has been newly acquired and is not yet universal. We cannot say positive- ly, yet it does seem as if in certain groups we could trace indications of a progressive increase or decrease in egg-pigmentation, which is actually in pro-