AMONG other rarities which I have been fortunate enough to procure since my arrival in the Bermudas, is a pelagic fish nest, similar in most respects to that which Agassiz has so recently described, and which was obtained by the American Expedition in the Gulf Stream in December last, while on the voyage to the West Indies. As I am very busy at present preserving and packing specimens, and the mail steamer nearly due, I have only time to send you (by way of St. Thomas) a brief description of my nest, which has been preserved in diluted alcohol. It was taken from a mass of gulf weed (Fucus natans) blown ashore about a month ago. This weed, by-the-bye, has been especially abundant about the Bermudas during the present winter, thousands upon thousands of tons having been cast ashore by the waves during the stormy weather which has prevailed. The size of the whole mass is about eight inches by five as it hangs suspended, the former measurement being its depth. The weed is thicker at the top, and is woven together by a maze of fine elastic threads, affording a raft, from which depends the clustering mass of eggs, which I cannot illustrate better than by asking your readers to imagine two or three pounds of No. 7 shot grouped together in bunches of several grains, and held in position by the elastic thread-work previously mentioned. These threads are amazingly strong, especially at their terminal bases on the fucus sprays, where several are apparently twisted together like the fibres of rope, and are admirably adapted to hold the mass in a position where it must always be subject, more or less, to violence, from the continued agitation of the waves in these stormy latitudes. The sea-weed is not only on the summit, but sundry sprays are interwoven with the mass of eggs, thereby rendering the fabric still more solid and secure. It is truly a wonderful specimen of Nature's handiwork; a house built without hands, resting securely on the bosom of the rolling deep.