EDIBLE BIRDS' NESTS. 327- 



of a microscopic alga, a species, probably new, of Glaeocapsa ; whilst 

 the edible nests from these caves, according to a cliemical and micro- 

 scopical examination made by Mr. J. R. Green,^ have been shown to 

 be formed in the great mass of 'mucin, which is the chief constituent 

 of the mucous secretions of animals. After exaraininQf various 

 specimens of edible nests from other localities, Mr. Green subse- 

 quently confirmed the results of his first experiments. The nest- 

 substance, as he unhesitatingly states, is composed of mucin, or of a 

 body closely related to it.^ So far, therefore, there would appear to 

 be but little evidence to support the view of Mr. Pryer that the 

 species of alga, which he found incrusting the rock in the vicinity 

 of the Borneo caves, supplied the material for the construction of 

 the nests of the swiftlets. However, before proceeding to state my 

 own opinion on the matter, I will refer briefly to my observations in 

 the Solomon Islands relating to this question. 



A species of CoUocalia, which usually frequents inaccessible sea- 

 caves and cliffs, is frequently to be observed on the coasts of the 

 islands of this group. The natives of Treasury Island call this bird 

 " kin-kin ; " but they have no knowledge of the nutrient qualities 

 of the substance of which it builds its nest, and they were much 

 amused when I told them of its being a Chinese luxury. I only 

 came uuon the nests of this bird on one occasion, and that was in 

 •some caves on Oima Atoll in Bougainville Straits. A desciiption of 

 these caves will be here unnecessar}''. As in the instance of the 

 birds of the Borneo caverns, these swiftlets shared their retreats 

 with a number of large bats, the accumulation of whose droppings 

 had produced a thick reddish -brown deposit on the floors of the 

 caves. The nests, which were formed for the most part of fibres 

 derived evidently from the vegetable drift ^ at the mouths of the 

 caves, were thickly incrusted with the gelatinous incrustation which 

 projected as winglets from the sides and fastened them to the rock. 



A reddish soft gelatinous incrustation occurred on the faces of 

 some of the cliffs in the vicinity of the caves. It was composed of 

 an aggregation of the cells of a microscopic unicellular alga which 

 measure -jtoo^ ^^ ^^ inch in diameter. Unfortunately the specimens 

 of this growth which I collected have been mislaid, but there can 

 be little doubt that it is similar to the "funcroid growth " which Mr. 



iProc. Zool. Soc, 1SS4, p. .532. 



2 ' Nature," Dec. 11th, 1884 and May, 27th, 1886. 



3 The husks of pandanus seeds more particularly. 



