The group Brachiopoda owes its chief interest to the immense variety and great antiquity of its fossil forms. Whereas at the present time the number of extant species amounts to but about 120, Davidson in his admirable monograph[410] on the British Fossil Brachiopoda has enumerated close upon 1000 fossil species, found within the limits of the United Kingdom alone.
The amount of interest that the group in question has excited amongst naturalists is evinced by the invaluable Bibliography of Brachiopoda, prepared by the same author and his friend W. H. Dalton.[411] This monument of patient research contains over 160 quarto pages, each with the titles of from eighteen to twenty separate papers dealing with Brachiopods, published between the years 1606 and 1885.
Probably the first reference to Brachiopods in zoological literature is to be found in a work entitled Aquatilium et Terrestrium aliquot Animalium, published in the year 1606 by Prince Fabio Colonna at Rome. This work contains the first description of a Brachiopod under the name of Concha diphya. In a second edition, which is not so rare in our libraries as the first, the author mentions three more species of Brachiopods. Towards the end of the same century, Martin Lister of Oxford, in his Historia sive Synopsis methodica Conchyliorum which appeared in parts, described and figured a considerable number of Brachiopods, which, under the name of Anomia, were until the present century regarded as Molluscs, and placed in the subdivision Pelecypoda (Lamellibranchiata).
The first satisfactory figure and description of a Terebratula were published in the year 1766, in Pallas’ Miscellanea Zoologica, still under the name Anomia. In 1781 O. F. Müller figured a Crania, under the name Patella anomala, the generic name being subsequently altered by Cuvier into Orbicula.
Bruguière in the year 1789 was the first to recognise the relationship between Lingula and the other Brachiopods. He for the first time saw the stalk of this genus, and compared it with that of the stalked Barnacles, a class of animals which has been more than once associated with our group.
Cuvier in his Mémoire sur l’Anatomie de la Lingule, 1797, gave the first account of the internal anatomy of a Brachiopod. The same naturalist first described the nephridia, although his mistake in considering them lateral hearts was not rectified until the middle of the present century, when Huxley pointed out that these structures serve as excretory ducts for the genital products.
Duméril in 1807 proposed the somewhat unfortunate name of Brachiopoda; and although efforts have been made by de Blainville, who suggested Palliobranchiata, and more recently by Haeckel, who proposed Spirobranchiata, to arrive at a name which would be both grammatically and physiologically more correct, the older name has maintained its position, and is now universally in use.
In 1834 and 1835 Professor Owen published the results of his researches into the anatomy of the Brachiopoda. He investigated in these years the structure of Waldheimia flavescens, of a species of Lingula and of a Discina, called by him Orbicula. He regarded the group as midway between the Pelecypoda and the Ascidians. The structure of Lingula was further investigated by Carl Vogt, who in 1851 also supported the view that the Brachiopoda were related to the Mollusca. But already in 1847 and 1848 Steenstrup had thrown doubts upon this relationship, and had maintained that the Order was more closely related to certain members of the Chaetopoda, a view which afterwards found its ablest supporter in the American naturalist Morse.
D’Orbigny seems to have been the first observer who drew attention to the resemblances alleged to exist between the Brachiopoda and the Polyzoa, and Hancock, in his masterly works On the Anatomy of the Fresh-water Bryozoa (Polyzoa) and in his Organisation of the Brachiopoda, dwelt on these resemblances, and placed the Brachiopoda between the Polyzoa on the one hand and the Ascidians on the other; a collocation which subsequently resulted in their inclusion in the now discarded group of Molluscoidea.
In 1854 Huxley[412] published what is, with the possible exception of Hancock’s monograph, mentioned above, the most important work upon the anatomy of the Brachiopoda with which we are acquainted. He corrected numerous errors of his predecessors and added many new facts to our knowledge of the group. He was the first to describe the true nature of the lateral hearts of Cuvier, and to describe the true heart, afterwards so carefully figured by Hancock.