December. i896. ZOOLOGY SINCE DARWIN. 365 



of lists, the perusal of which gave the zoologist no more food for 

 thought than did the sight of a menagerie. 



In this respect the new teaching of the theory of descent made a 

 revolution, by first rendering possible a scientific treatment of zoogeo- 

 graphical facts. The faunistic character of a region is decided by its 

 geographical age, and also by the phylogenetic stage of evolution of 

 the animal world at the time of its settlement, and by its changing 

 geographical relations to other faunal districts, during the different 

 phases of the earth's history. It follows therefrom that it is not so 

 much phenomena due to adaptation, but rather crises in the history 

 of the stock, which decide the typical character of a fauna. Thus, 

 zoogeography becomes an important branch of phylogeny.^ A. R. 

 Wallace, in his celebrated work, " The Geographical Distribution of 

 Animals," laid stress on this point, and thereby became the teacher 

 of modern zoogeography. A necessary condition, however, to the 

 further progress of this science is the utmost exactness in the 

 wearisome details of systematic descriptions of species. 



Descriptive systematics have benefited from the new method, 

 indirectly much more than directly, because the new teaching 

 awakened general interest in zoology and botany, and thus directed 

 more working energy into those channels than there ever was before. 

 Moreover, it is easy to prove that the colossal addition to our hst of 

 animal forms — about 50,000 in 1832, to-day about 150,000 — is due no 

 less to the increase of means of communication and to the evolution 

 of geography. It was not till the latter, from being the handmaid of 

 history, passed into an independent science, and oceanographic 

 questions came to the fore, that those big expeditions were under- 

 taken, which form another characteristic of this period of zoology. 

 One is involuntarily reminded of the time of Piso, Marcgravius, and 

 Bontius, who, at the beginning of the seventeenth century, showed to 

 wondering mankind the pictures of the Dronte and the Homo 

 silvestris, from " The Two Indies," when one realizes that the 

 "Challenger" Expedition of 1873-76 (concerned chiefly only with 

 marine forms), brought back nearly 8,000 new species of animals. 

 The description of these resulted in hundreds of new genera, families, 

 and orders, and occupied sixty zoologists of all civilized countries 

 twenty years, appearing finally in thirty-two quarto volumes, with 



2 Genealogical relations are brought especially into prominence in geographical 

 distribution in those cases where there exists a proportion between the geographical 

 separation and the amount of morphological difference. This important law was 

 first formulated by H. Spitzer in his excellent " Beitragen zur Descendenz Theorie" 

 (Leipzig, 1886), and proved by him (pp. 259 et seq.) for the orders of apes and 

 ostrich-hke birds. This proportion should also be demonstrable in many other 

 groups of animals. It may here be pointed out that one of the most decided 

 opponents of the Theory of Descent with Modification (A. Wigand), made his agree- 

 ment with the latter dependent upon the possibility of such a relation between 

 geographical separations and morphological dififerences being proved. (A. Wigand, 

 " Der Darwinismus und die Naturforschung Newton's und Cuvier's," Braunschweig, 

 1874-77) 



