|DE PROFUNDIS / Introduction (2) / Allophora oculina & Bathycrinus gracilis
C. WYVILLE THOMSON - "THE DEPTHS OF THE SEA"
|THE DEPTHS OF THE SEA
C. WYVILLE THOMSON
The late Professor Edward Forbes appears to have been the first who undertook the systematic study of Marine Zoology with special reference to the distribution of marine animals in space and in time. After making himself well acquainted with the fauna of the British seas to the depth of about 200 fathoms by dredging, and by enlisting the active co-operation of his friends-among whom we find MacAndrew, Barlee, Gwyn Jeffreys, William Thompson, Robert Ball, and many others, entering enthusiastically into the new field of N atural History inquiry - in the year 1841 Forbes joined Capt. Graves, who was at that time in command of the Mediterranean Survey, as naturalist. During about eighteen months he studied with the utmost care the conditions of the AEgean and its shores, and conducted upwards of one hundred dredging operations at depths varying from 1 to 130 fathoms. In 1843 he communicated to the Cork meeting of the British Association an elaborate report on the Mollusca and Radiata of the AEgean Sea, and on their distribution considered as bearing on Geology. Three years later, in 1846, he published in the first volume of the ' Memoirs of the Geological Survey of Great Britain,' a most valuable memoir upon the Connection between the existing Fauna and Flora of the British Isles, and the geological Changes which have affected their Area, especially during the Epoch of the N orthern Drift. In the year 1859 appeared the Natural History of the European Seas by the late Professor Edward Forbes, edited and continued by Robert Godwin Austens In the first hundred pages of this little book, Forbes gives a general outline of some of the more important of his views with regard to the distribution of marine forms. The remainder of the book is a continuation by his friend Mr. Godwin Austen, for before it was finished an early death had cut short the career of the most accomplished and original naturalist of his time.
I will give a brief sketch of the general results to which Forbes was led by his labours, and I shall have to point out hereafter, that although we are now inclined to look somewhat differently on certain very fundamental points, and although recent investigations with better appliances and more extended experience have invalidated many of his conclusions, to Forbes is due the credit of having been the first to treat these questions in a broad philosophical sense, and to point out that the only means of acquiring a true knowledge of the rationale of the distribution of our present fauna, is to make ourselves acquainted with its history, to connect the present with the past. This is the direction which must be taken by future inquiry. Forbes, as a pioneer in this line of research, was scarcely in a position to appreciate the full value of his work. Every year adds enormously to our stock of data, and every new fact indicates more clearly the brilliant results which are to be obtained by following his methods, and by emulating his enthusiasm and his indefatigable industry.
Forbes believed implicitly, along with nearly all the leading naturalists of his time, in the immutability of species. He says (Natural History of the British Seas, p. 8), "Every true species presents in its individuals, certain features, specific characters, which distinguish it from every other species; as if the Creator had set an exclusive mark or seal on each type." He likewise believed in specific centres of distribution. He held that alI the individuaIs composing a species had descended from a single progenitor, or from two, according as the sexes might be united or distinct, and that consequently the idea of a species involved the idea of the relationship in alI the individuaIs of common descent; and the converse, that there could by no possibility be community of descent except in living beings which possessed the same specific characters. He supposed that the original individual or pair was created at a particular spot where the conditions were suitable for its existence and propagation, and that the species extended and migrated from that spot on alI sides over an area of greater or less extent, until it met with some natural barrier in the shape of unsuitable conditions. No specific form could have more than a single centre of distribution. If its area appeared to be broken up, a patch not in connection with the original centre of distribution occurring in some distant locality, it was accounted for by the formation, through some geological change after the first spread of the species, of a barrier which cut off a part of its area; or to some accidental transport to a place where the conditions were sufficiently similar to those of its natural original habitat to enable it to become naturalized. No species once exterminated was ever recreated, so that in those few cases in which we find a species abundant at one period over an area, absent over the same area for a time, and recurring at a later period, it must be accounted for by a change in the conditions of the area which forced the emigration of the species, and a subsequent further change which permitted its return.
Forbes defined and advocated what he called the law of representation. He found that in all parts of the world, however far removed, and however completely separated by natural barriers, where the conditions of life are similar, species and groups of species occur which, although not identical, resemble one another very closely; and he found that this similarity existed likewise between groups of fossil remains, and between groups of fossils and groups of recent forms. Admitting the constancy of specific characters, these resemblances could not be accounted for by community of descent, and he thus arrived at the generalization, that in localities placed under similar circumstances, similar though specifically distinct specific forms were created. These he regarded as mutually representative species.