BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 211 



has brought about. . . . Those whose acquired habits 

 have become thoroughly ingrained are now pretty constant in 

 their adherence to a single plan of architecture; but the 

 Violet-green Swallow, for instance, at present nests in a very 

 loose fashion, according to circumstances." * 



The statement made in 1870 by the distinguished 

 naturalist Pouchet to the effect that within the same interval 

 of half a century the house-swallow had materially altered its 

 mode of nest-building at llouen,f was subsequently shown by 

 M. Noulet to be erroneous;; but this passage which I have 

 quoted from Captain Elliott Coues is sufficient to show that 

 facts analogous to those stated by M. Pouchet have occurred 

 among many species of the swallow tribe. 



In " Animal Intelligence " I gave some cases of the 

 remarkable intelligence which is displayed by certain birds 

 when they remove their eggs or their young from places 

 where they have been disturbed (pp. 288-9), and I added the 

 remark that it is easy to see that if any particular bird is in- 

 telligent enough, as in the cases quoted, to perform this 

 adjustive action of conveying young — whether to feeding- 

 grounds, as in the case of the hen, or from sources of danger, 

 as in the case of partridges, blackbirds, and goat-suckers — 

 inheritance and natural selection might develop the originally 

 intelligent adjustment into an instinct common to the species. 

 And it so happens that this has actually occurred in at least 

 two species of birds — viz., the woodcock and wild duck, both 

 of which have been repeatedly observed to fly with their 

 young to and from their feeding-ground. 



Since writing the above, I have found among Mr. Darwin's 

 MSS a letter from Mr. Haust, dated New Zealand, December 

 '.Hli, 1862, and stating that the "Paradise Duck," which 

 naturally or usually builds its nest along the rivers on the 

 ground, has been observed by him on the east of the island, 

 when disturbed in their nests upon the ground, to build " new 

 ones on the tops of high trees, afterwards bringing their young 

 ones down on their backs to the water," and exactly the 

 same thing has been observed of the wild ducks of Guiana § 

 Now, if intelligent adjustment to peculiar circumstances is 



• Bird* of Colorado Valley, pp. 892 I + Comptet Rendu*, l\\, \>. 492. 

 X Ibid., \\\\, p. 78, In the ffrti edition of Animal Intelligence I quote I 

 tin- itatemenl of rouohel irithoul knowing that it had been questioned. 

 § Bee QeoL Jonm., roL It, p. 3Jo. 



