APPENDIX. 3G5 



so on, till we arrive at marvellous structures, rivalling the 

 weavers' art. 



Even in so singular a nest as that of the Hiriiiido (Col- I 

 localia csculcnta), eaten by the Chinese, 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, 

 very like pure gum arabic, 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 absorbs 

 water and softens : examined under the microscope it 

 exhibits no structure, except traces of lamination, and very 

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

 are very conspicuous in small dry fragments, and some bits 

 looked almost like vesicular 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 Mr. G. R. 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 

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

 Macgillivray 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 

 N. Americaf another species of Swift causes its nest to 

 adhere against the Vertical wall of B chimney, and builds it 

 of small Sticks placed parallel and agglutinated together 



• [In tin- MS H blank it here intentional!] left for the subsequent filling 

 in of an appropri ate word. G-. J. B.1 



+ For Cypselui murariiu tee Macgillivray, British Hints, toI. iii, 1840, 



SB25, I ' "v. see Mr, Peabody's excellent paper on the Birdi 



ihussetts in the Boston Journal of X<it. Si*t., vol. iii. p. is?. Iff. K. 

 Robert (Cotnptet Rendu*, quoted in .tun*, and .1/"/. of If at. Witt., vol. nil, 

 1^12. |i 176) found thai the nests of the Hirundo riparia, made in tin- 

 gravellj l>;ink* of tli" Volga, bad their upper surface* plaatered with -\ yellow 

 it ii i n 1. 1 1 substance, which be imagined i" be fishes' spawn. Could be bare 

 dcen the species, for there is no reason to suppose our bank-martin bas 

 any turd babitP This won if | be ■ rerj remarkable rariation of instinct, if it 

 could !'<• proved) and the more remarkable thai this bird be! kdif« 



ferenl sub-family from the Swift* and Collocalia. JTel I am inclined to 

 believe it. lor it has been affirmed with apparent truth thai the Bouae^martin 

 naoisti as the mud, with which it innlila n.-^ nest, with adhi live saliva. 



