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Rh special theory of saltations, or of sudden modifications of structure through changes of environment, especially through the direct influences of temperature and atmosphere. He clearly set forth also the phenomena of analogous or parallel adaptation.

It was Alcide Dessalines d'Orbigny (1802-1857) who pushed to an extreme Cuvier's ideas of the fixity of species and of successive extinctions, and finally developed the wild hypothesis of twenty-seven distinct creations. While these views were current in France, exaggerating and surpassing the thought of Cuvier, they were strongly opposed in Germany by such authors as Ernst Friedrich von Schlotheim (1764-1832) and Heinrich Georg Bronn (1800-1862); and the latter demonstrated that certain species actually pass from one formation to another.

In the meantime the foundations of palaeobotany were being laid (1804) by Ernst Friedrich von Schlotheim (1764-1832), (1811) by Kaspar Maria Sternberg (1761-1838) and (1838) by Théophile Brongniart (1801-1876).

Following Cuvier's Recherches stir les ossemens fossiles, the rich succession of Tertiary mammalian life was gradually revealed to France through the explorations and descriptions of such authors as Croizet, Jobert, de Christol, Eymar, Pomel and Lartet, during a period of rather dry, systematic work, which included, however, the broader generalizations of Henri Marie Ducrotay de Blainville (1778-1850), and culminated in the comprehensive treatises on Tertiary palaeontology of Paul Gervais (1816-1879). Extending the knowledge of the extinct mammals of Germany, the principal contributors were Georg August Goldfuss (1782-1848), Georg Friedrich von Jaegar (1785-1866), Felix F. Plieninger (1807-1873) and Johann Jacob Kaup (1803-1873). As Cuvier founded the palaeontology of mammals and reptiles, so Louis Agassiz's epoch-making works Recherches sur les poissons fossiles (1833-1845) laid the secure foundations of palaeichthyology, and were followed by Christian Heinrich Pander's (1794-1865) classic memoirs on the fossil fishes of Russia. In philosophy Agassiz was distinctly a disciple of Cuvier and supporter of the doctrine of special creation, and to a more limited extent of cataclysmic extinctions. Animals of the next higher order, the amphibians of the coal measures and the Permian, were first comprehensively treated in the masterly memoirs of Christian Erich Hermann von Meyer (1801-1869) beginning in 1829, especially in his Beiträge zur Petrefactenkunde (1829-1830) and his Zur Fauna der Vorwelt (4 vols., 1845-1860). Successive discoveries gradually revealed the world of extinct Reptilia; in 1821 Charles König (1784-1851), the first keeper of the mineralogical collection in the British Museum, described Ichthyosaurus from the Jurassic; in the same year William Daniel Conybeare (1787-1857) described Plesiosaurus; and a year later (1822) Mosasaurus; in 1824 William Buckland described the great carnivorous dinosaur Megalosaurus; while Gideon Algernon Mantell (1790-1852) in 1848 announced the discovery of Iguanodon. Some of the fossil Reptilia of France were made known through St Hilaire's researches on the Crocodilia (1831), and those of J. A. Deslongchamps (1794-1867) and his son on the teleosaurs, or long-snouted crocodiles. Materials accumulated far more rapidly, however, than the power of generalization and classification. Able as von Meyer was, his classification of the Reptilia failed because based upon the single adaptive characters of foot structure. The reptiles awaited a great classifier, and such a one appeared in England in the person of Sir Richard Owen (1804-1892), the direct successor of Cuvier and a comparative anatomist of the first rank. Non-committal as regards evolution, he vastly broadened the field of vertebrate palaeontology by his descriptions of the extinct fauna of England, of South America (including especially the great edentates revealed by the voyage of the “Beagle”), of Australia (the ancient and modern marsupials) and of New Zealand (the great struthious birds). His contributions on the Mesozoic reptiles of Great Britain culminated in his complete rearrangement and classification of this group, one of his greatest services to palaeontology. Meanwhile the researches of Hugh Falconer (1808-1865) and of Proby Thomas Cautley (1802-1871) in the sub-Himalayas

brought to light the marvellous fauna of the Siwalik hills of India, published in Fauna antiqua Sivalensis (London, 1845) and in the volumes of Falconer's individual researches. The ancient life of the Atlantic border of North America was also becoming known through the work of the pioneer vertebrate palaeontologists Thomas Jefferson (1743-1826), Richard Harlan (1796-1843), Jeffries Wyman (1814-1874) and Joseph Leidy (1823-1891). This was followed by the revelation of the vast ancient life of the western half of the American continent, which was destined to revolutionize the science. The master works of Joseph Leidy began with the first-fruits of western exploration in 1847 and extended through a series of grand memoirs, culminating in 1874. Leidy adhered strictly to Cuvier's exact descriptive methods, and while an evolutionist and recognizing clearly the genetic relationships of the horses and other groups, he never indulged in speculation.

The history of invertebrate palaeontology during the second period is more closely connected with the rise of historic geology and stratigraphy, especially with the settlement of the great and minor time divisions of the earth's history. The path breaking works of Lamarck were soon followed by the monumental treatise of Gérard Paul Deshayes (1795-1875) entitled Descriptions des coquilles fossiles des environs de Paris (1824-1837), the first of a series of great contributions by this and other authors. These and other early monographs on the Tertiary shells of the Paris basin, of the environs of Bordeaux, and of the sub-Apennine formations of Italy, brought out the striking distinctness of these faunas from each other and from other molluscan faunas. Recognition of this threefold character led Deshayes to establish a threefold division of the Tertiary based on the percentage of molluscs belonging to types now living found in each. To these divisions Lyell gave in 1833 the names Eocene, Miocene and Pliocene.

James Hutton (1726-1797) had set forth (1788) the principle that during all geological time there has been no essential change in the character of events, and that uniformity of law is perfectly consistent with mutability in the results. Lyell marshalled all the observations he could collect in support of this principle, teaching that the present is the key to the past, and arraying all obtainable evidence against the cataclysmic theories of Cuvier. He thus exerted a potent influence on palaeontology through his persistent advocacy of uniformitarianism, a doctrine with which Lamarck should also be credited. As among the vertebrates, materials were accumulating rapidly for the great generalizations which were to follow in the third period. De Blainville added to the knowledge of the shells of the Paris basin; Giovanni Battista Brocchi (1772-1826) in 1814, and Luigi Bellardi (1818-1889) and Giovanni Michelotti (born 1812) in 1840, described the Pliocene molluscs of the sub-Apennine formation of Italy; from Germany and Austria appeared the epoch-making works of Heinrich Ernst Beyrich (1815-1896) and of Moritz Hoernes (1815-1868).

We shall pass over here the labours of Adam Sedgwick (1785-1873) and Sir Roderick Murchison (1792-1871) in the Palaeozoic of England, which because of their close relation to stratigraphy more properly concern geology; but must mention the grand contributions of Joachim Barrande (1799-1883), published in his Système silurien du centre de la Bohème, the first volume of which appeared in 1852. While establishing the historic divisions of the Silurian in Bohemia, Barrande also propounded his famous theory of “colonies,” by which he attempted to explain the aberrant occurrence of strata containing animals of a more advanced stage among strata containing earlier and more primitive faunas; his assumption was that the second fauna had migrated from an unknown neighbouring region. It is proved that the specific instances on which Barrande's generalizations were founded were due to his misinterpretation of the overturned and faulted strata, but his conception of the simultaneous existence of two faunas, one of more ancient and one of more modern type, and of their alternation in a given area, was based on sound philosophical principles and has been confirmed by more recent work.