ICG mr. W. h. hxjdson on the [Mar. 3, 



sary to its own), by combining in imagination all known parasitical 

 habits, eliminating every offensive quality or circumstance, and at- 

 tributing such others in tbeir place as we should think fit, our con- 

 ception would probably fall far short in simplicity, beauty, and com- 

 pleteness 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 selec- 

 tion could not lead;" for it seems absolutely perfect. 



XI. Occasional aberrant procreant habits. — When considering 

 the parasitical procreant habits of birds, every irregularity in 

 the breeding-habits of other species becomes interesting. I there- 

 fore 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 bonuriensis 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 ob- 

 serve seasons in laying do not finish tbeir 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 (Proyne tapera) 

 breeding in November ; these birds have succeeded, immediately after 

 arriving, in possessing themselves of ovens of the Farnarii, 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 iu a few genera- 

 tions did they possess it. Only when the egg is already in the ovi- 

 duct 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 



