AITEXDIX. 365 



SO on, till we arrive ;it marvellous structures, rivalling the 

 weavers' art. 



Even in so singular a nest as that of the Hirundo {Col- 

 localia csculcnta), eaten by the Cliinese, we can, I think, trace 

 the stages by which the necessary instinct has been acquired. 

 The nest is composed of a brittle white translucent substance, 

 \QYj like pure gum aral)ic, or even glass, lined with adherent 

 feather-down. The nest of an allied species in the British 

 Museum consists of irregularly reticulated fibres, some as 

 fine as * of the same substance ; in another species 



bits of sea-weed are agglutinated together with a similar 

 substance. This dry mucilaginous matter soon al)Sorbs 

 water and softens : examined under the microscope it 

 exhibits no structure, except traces of lamination, and ver}- 

 generally joear-shaped bubbles of various sizes ; these, indeed, 

 are very conspicuous in small dry fragments, and some bits 

 looked almost like ^'esicular lava. A small pure piece put 

 into flame crackles, swells, does not readily burn, and smells 

 strongly of animal matter. The genus Collocalia, according 

 to ]\Ir. G. E. Gray, to whom I am much obliged for allowing 

 me to examine all the specimens in the British Museum, 

 ranks in the same sub-family with our common Swift. The 

 latter bird generally seizes on the nest of a sparrow, but Mr. 

 ]\Iacgillivray has carefully described two nests in which 

 the confusedly fitted materials were agglutinated together 

 by extremely thin shreds of a substance which crackles 

 but does not readily burn when put into a flame. In 

 X. Americaf another species of Swift causes its nest to 

 adhere against the vertical wall of a chinniey, and builds it 

 of small sticks placed parallel and agglutinated together 



* [In tlie MS a blank is liere intentionally left for tlie subseqnont filling- 

 in of an appropriate word. — Gr. J. R.] 



t For Cypselus murarliifi see Macgillivray, Br!tii<h Birch, vol. iii, 1840, 

 ]). 625. For C. pelasgiua, see Mr. Peabodv's excellent paper on the Birds of 

 .Massacbussetts in the Boston Journal of Xat. Hist., vol. iii, p. 187. M. E. 

 Robert {Compter Renduft, qiioted in Anns, and Mag. of Nat . Hist., vol. viii, 

 1812, p. 476) found that tlie nests of the Hirundo riparia, made in the 

 gravelly banks of the Volga, had tlieir upper surfaces plastered with a yellow 

 animal substance, which he imagined to be fishes' spawn. Could he liave 

 mistaken the species, for tliere is no reason to suppose our bank-martin lias 

 any such habit? This woidd be a very remarkable variation of instinct, if it 

 coidd be proved ; and the more remarkable that this bird belongs to a dif- 

 ferent sub-family from the Swifts and Collocalia. Yet I am inclined to 

 believe it, for it has been afRinned with apparent truth that the House-martin 

 moistens the mud, with which it builds its nest, with adhesive saliva. 



