We remained in the cave for about half an hour, during which time the birds came and went indifferent to our presence. As far as I am aware members of the species never rest save in their headquarters, clinging to the roof or the nests and never utter a sound except the reassuring, prattle upon alighting on the edge of the nest. It was interesting to note that while many young birds were fluttering about in the cave none occupied a nest, and eggs were in successive stages of incubation, as proved by appearance and test. The fact that the nests of these swifts are cemented with coagulated saliva establishes analogy with that other member of the family which builds in the caves of frowning precipices near the sea, making edible nests greatly appreciated by Chinese gourmands, some of whom maintain the fantastic theory that the swift catches quantities of a small, delicately flavoured fish which it exposes on rocks until desiccated, to be afterwards compounded into nests. The ancients were wont to believe in the existence of hostile mutuality between the swifts and the bêche-de-mer, though they have little in common in respect of appearance, attributes, and habits. If memory serves, one of the genera had the specific title of HIRUNDO, founded on the faith that the swift, by flying over the sea-slug exposed by receding tide, and vexing it by jeers, caused it to exude glutinous threads which the swift seized and bore away to its cave to be consolidated and moulded into a nest. To the fable was appended a retributive moral, viz., that the bêche-de-mer occasionally revenged itself by expelling such a complicated mass of gluten that it became a net for the capture of the swift, which was slowly assimilated by its enemy. The Chinese, it may be said, with but slight perversion of fact, show equal partiality for the respective emblems of speed and sloth. Since the dates mentioned it has been ascertained by personal observation that the breeding season of the swiftlet extends over four months, during which probably four young are reared, each clutch being single. The nests do not provide accommodation for more than one chick, which before flight is obviously top large for its birthplace. Looking down into the cave, the eggs well advanced towards incubation seem to have a slight phosphorescent glow. The earliest date so far recorded of the discovery of a newly laid egg is October 14th, but there is reason to believe that the breeding season begins at least a month earlier. On January 10th this year (1910) half the nests in the cave originally described contained eggs, in most of which (judging by opacity) incubation was far advanced, while in several were young birds, some newly hatched, others apparently ready to depart from their gloomy, foul-smelling quarters. These latter clung so determinedly to their nests with needle-like toes that the force necessary to remove them would certainly have caused injury.