Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/864

Rh 814 ZOOLOGY Develop ment of new species. Geo graphi cal dis tribution of ani mals. Study of marine fauna. We have now traced the history of the morphography of animals so as to show that increasingly in successive epochs independent branches of knowledge have been brought to bear on the consideration of the main problem, namely, the discrimination of the kinds and the relations to one another of animal forms. Before glancing at the history of the remaining branches of zoological science, which have had an independent history whilst ultimately contributory to taxonomy and morphography, it may be briefly pointed out that the accumulation of knowledge with regard to the distribution of animal forms on the earth s surface and in the seas has progressed simultane ously with the discrimination of the mere forms of the species themselves, as has also the knowledge derived from fossilized remains as to the characters of former in habitants of the globe. Both these subdivisions of mor phography have contributed to the establishment of Dar winism, the one (palaeontology) by direct evidence of organic evolution in time, the other (zoo-geography) in a more indirect way. Alfred Russell Wallace stands prominently forward as a naturalist -traveller who by his observations, chiefly on Lepidopterous Insects, in both South America and the Malay Archipelago, was led to the conclusion that a pro duction of new species is actually going on, and that, too, by means of a process of natural selection of favourable variations. Wallace and Darwin, who each recognized cordially and fully the other s work, laid their views before the Linnean Society on the same day in 1859. The facts of the geographical distribution of animals were systematized, and great zoo-geographical provinces first clearly recognized, by P. L. Sclater in 1857. The application of the Darwinian theory to the facts tabulated by Sclater, combined with a knowledge of the distribution of animals in past geological periods, has led to a full explanation of the migrations of terrestrial animals, and has furnished a striking corroboration of the sufficiency of the doctrine of organic evolution, as reformed by Darwin, to account for all the phenomena of zoology. The study of the marine fauna by means of the dredge and trawl had been enthusiastically prosecuted by British, French, and Scandinavian naturalists in the two decades before Darwin s book; the collection of forms, the discovery of new species, and the recording of their bathymetrical and local distribution had produced a great mass of know ledge through the labours of E. Forbes, Gwyn-Jeffreys, Sars, Quatrefages, Norman, and others. The post-Dar winian developments of this line of inquiry have been two. In the first place, dredging and trawling have been extended by the aid of steamships of the Norwegian, British, Ameri can, French, and Italian navies into greater depths than were previously supposed to contain living things. New species and genera, and a vast extension of knowledge as to distribution, have been the outcome of these expeditions, connected with the names of G. O. Sars and Daniellsen in Norway, of Alex. Agassiz in America, and of Carpenter and Wyville Thomson in Great Britain. It is worthy of note that the practical demand for sounding the Atlantic in connexion with the laying of the first deep-sea telegraph- cable is what led to these explorations, the first recognition of life at these great depths in the ocean being clue to Dr Wallich, who accompanied a sounding expedition in 1860 to the North Atlantic, and to Prof. Fleeming Jenkin, who in the same year acted as engineer in raising the sub marine cable between Sardinia and Africa, upon which living corals were found. In the second place, the study of marine zoology has, since the publication of the Origin of Species, been found to require more complete arrange ments in the form of laboratories and aquaria than the isolated vacation student could bring with him to the Expedi tions for local study of fauna. seaside. Seaside laboratories have come into existence : the first was founded in France by Coste (1859) at Concarneau (Brittany), again with a practical end in view, viz., the study of food -fishes with an aim to pisciculture. The demand for a knowledge of the embryology of all classes of animals, and for further facts as to the structure and life- history of the minuter microscopic or very delicate forms of marine life, is what has determined the multiplication of these marine &quot; stations.&quot; The largest and best supported pecuniarily is that founded at Naples by Anton Dohrn in 1872 ; others exist at Trieste, Villefranche, Cette, and at New Haven and Beaufort in the United States, whilst a large laboratory, on a scale to compare with that at Naples, has this year (1888) been opened at Plymouth by the Marine Biological Association of the United Kingdom. Another result of the stimulus given to zoological re search by Darwin s work is the undertaking of voyages to distant lands by skilled anatomists for the purpose of studying on the spot, and with all the advantages of abund ant and living material, the structure, and especially the embryology, of rare and exceptionally interesting forms of animal life. In the pre- Darwinian period of this century zoologists who were convinced of the importance of anatomical and embryological study were still content to study specimens immersed in spirit and brought home, often imperfectly preserved, by unskilled collectors, or to confine their attention to such species as could be procured in Europe. Before Cuvier, as we have already pointed out, attention was, with rare exceptions, limited to the dried skeletons and external forms of animals. Now, however, the enterprising zoologist goes to the native land of an interesting animal, there to study it as fully as possible. The most important of these voyages has been that of W. H. Caldwell of Cambridge to Australia (1885-86) for the purpose of studying the embryology of the Monotrema and of Ceratodus, the fish-like Dipnoon, which has resulted in the discovery that the Monotrema are oviparous. Similarly Adam Sedgwick proceeded to the Cape in order to study Peri]xitus, Bateson to the coast of Maryland to study Balanoglossus, and the brothers Sarassin to Ceylon to in vestigate the embryology of the Coecilia. The task of the zoologist has changed and developed in every succeeding period. Pure morphography has long ceased to be a chief line of research ; and now even the preoccupation produced by the addition to it of the study of cellular embryology is about to undergo a modification by the demand for knowledge of the facts of heredity and adaptation in greatly extended detail. ZOO-MECHANICS, ZOO-PHYSICS, ZOO-CHEMISTRY. The development of that knowledge of the structure of Study of the human body, and of the chemical and physical pro- anatomy cesses going on in it, which is necessary for the purposes of a ? the medical art forms a distinct history, which has both influenced and been influenced by that of other branches of zoology. The study of the structure and composition of the body of man and of the animals nearest to him was until fifty years ago one with the inquiry into the activities of those parts, and indeed the separation of anatomy and physiology has never been really carried out. For convenience of teaching, the description of the coarser anatomy of the human body has been in modern universities placed in the hands of a special professor, theoretically condemned to occupy himself with the mere formal details of structure, whilst the professor of physiology has usually retained what is called &quot;microscopic anatomy,&quot; and necessarily occupies himself with as much structural anatomy as is required for a due description of the functions of organs and the properties of tissues. It would seem that in our medical schools and universities these arrange-