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Show 166 MR. W. H. HUDSON ON T H E [Mar. 3, sary to its own), by combining in imagiuation all known parasitical habits, eliminating every offensive quality or circumstance, and attributing such others in their place as we should think fit, our conception would probably fall far short in simplicity, beauty, and completeness to the real instinct of the M. rufoaxillaris. Instead of laying its eggs promiscously in every receptacle that offers, it selects the nest of a single species; so that its selective instinct is related to the adaptive resemblance in its eggs and young to those of the species on which it is parasitical. Such an adaptive resemblance could not exist if it laid its eggs in the nests of other species, and it is certainly a circumstance eminently favourable to preservation. Then, there not being any such incongruity and unfitness as we find in nests into which other parasitical species intrude, there is no reason here to regard the foster-parent's affection as blind and stupid; the similarity is close enough to baffle the keenest sagacity. Nor can the instinct here appear in the light of an outrage on the maternal affection; for the young M. rufoaxillaris apparently possesses no superiority over his foster-brothers. He is not endowed with greater strength and voracity to monopolize the attentions of the foster-parents and to eject or otherwise destroy the real offspring; but being in every particular precisely like them, he has only an equal chance of being preserved. What the most philosophical of naturalists has remarked concerning the architecture of the hive-bee may be applied to this parasitical instinct:-" Beyond this stage of perfection natural selection could not lead;" for it seems absolutely perfect. X L Occasional aberrant procreant habits.-When considering the parasitical procreant habits of birds, every irregularity in the breeding-habits of other species becomes interesting. I therefore introduce a note on the occasional habit of wasting eggs of some species, and of more than one female laying in the same nest. The Molothrus bonariensis wastes many eggs ; so also do our two species of Rhea ; but in the former the parasitical habit is the immediate cause of the occasional habit. Birds that build and observe seasons in laying do not finish their nests precisely at the time when they are ready to drop their eggs, but some little time, often two or three or more days, beforehand ; if the nest is destroyed, the growth of the ova is arrested till a new nest is completed. Every summer we see here pairs of parasitical Martins (Progne tapera) breeding in November ; these birds have succeeded, immediately after arriving, in possessing themselves of ovens of the Furnarii, in which alone they breed; but in all the birds that have failed in their attacks on the Oven-birds and do not breed till December and January, the ova, though large, are in abeyance, and only become fully developed when the birds have seized on the ovens about which they have been long fluttering. This beautiful provision is not necessary in the Molothrus ; indeed it is obvious that it would prove fatal to the species in a few generations did they possess it. Only when the egg is already in the oviduct and the time for its exclusion approaches, the bird begins to look about for a receptacle; its failing to find one, or its being repulsed |