Having been engaged for some time past in the investigation of the anatomy of the Brachiopods, I beg to lay before the Royal Society the results of my labours; and I am the more anxious to do so as some differences of opinion have arisen among naturalists respecting the structure of these interesting animals. Four years ago I had occasion to dissect Waldheimina australis, Terebratulina caputserpentis and Lingula anatina , and was then struck with the peculiar appearance of the organs denominated hearts by Baron Cuvier, Professor Owen, and all subsequent writers on the subject. These so-called hearts seemed to me very unlike any molluscan heart that had ever come under my observation; and on attentive examination it became evident that they give off no arteries as they had been described to do; and moreover that their apices, from which the arteries were stated to pass, appeared to open externally. For these, and for other reasons, I was inclined to disbelieve in their cardiac nature, and to regard them rather as oviducts.