690 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



procedure in the investigation of fossil remains is evident in the character of 

 published work throughout Europe during the second quarter of the nine- 

 teenth century. 



Cuvier emphasized the occurrence of the more primitive forms of animal 

 life in the older geological formations and pointed out that extinct genera lived 

 at an earlier time than those of the Recent. However, he did not believe that 

 the living organisms had originated through the anatomical modifications of the 

 older forms. He considered that during the past history of the earth there had 

 been many sudden and violent disturbances of the crust which had resulted in 

 the submergence of vast areas of land and the reappearance from beneath the 

 ocean's surface of vast islands and continental masses. Destruction of the faunas 

 and floras accompanied these catastrophic movements. Following each catastrophe 

 a new and more advanced biologic fauna came into existence, the last of these 

 appearing about six thousand years ago. Translations of Cuvier's work into 

 several languages accentuated discussion of the problem. The Cuvierian concept 

 of immutability of species was opposed by several European naturalists who 

 held that new species might arise by the gradual modification of pre-existing 

 species as the result of changing environments. This became known as the theory 

 of mutability in contrast to that of immutability as advocated by Cuvier. 



Among the earliest strong supporters of the concept of mutability of species 

 was Lamarck, who developed the idea that the morphological characters of a 

 species might be subject to modification from generation to generation when 

 subjected to environmental stimuli and that such acquired characters could be 

 inherited. He recognized the morphological differences of extinct species from 

 a succession of epochs and compared them with species now living in nearby 

 areas and thus pointed out the possibility of the correlation of formations by the 

 use of fossils. His investigations were largely concerned with marine inverte- 

 brate fossils from the Tertiary deposits of the Paris Basin, which were described 

 (Lamarck, 1815-1822) in his important monograph on Natural History of In- 

 vertebrate Animals. This contribution, devoted largely to fossil mollusks, played 

 an important part in the foundation of scientific conchology. Although the La- 

 marckian concepts were accepted by an increasing number of European investi- 

 gators yet the Cuvierian ideas were strongly entrenched in scientific thinking 

 even beyond the middle of the nineteenth century and to a considerable extent 

 influenced the writings of d'Orbigny. 



Many significant contributions were made to the growing science of paleon- 

 tology during the early half of the nineteenth century. These consisted largely 

 of descriptions of fossil species and monographs of faunas from different for- 

 mations of Europe and North America, together with catalogues containing 

 named species. Among the important contributors were James Sowerby and 

 his son, James de Carle Sowerby, E. F. Schlotheim, H. G. Bronn, G. A. Gold- 

 fuss, A. d'Orbigny in Europe, and T. A. Conrad in North America. 



The mollusks of Great Britain were described and illustrated in a six-volume 

 work by the Sowerbys published from 1812 to 1846. This work was of great 

 value for further investigations in conchology and for a comparison of the Ter- 

 tiary faunas of Great Britain with those of France and other parts of Europe. 

 Contemporaneously in Germany Ernst von Schlotheim in 1820 published his 

 work Die Petrefadenkunde, in which many invertebrate fossils were figured 



