The work published by Messrs. Speyer deals only with the origin of the Central European Butterflies. The period during which our European species originated is not specified, but the authors believe that they had their home either in Southern Russia or Central Asia. The fact that the number of butterflies decreases very considerably as we proceed north-westward in Europe appears to them to substantiate these views. The apparent dislike evinced by butterflies to the damp Atlantic Coast climate, they think, clearly indicates that they had originated in a dry and more continental climate. The history of the North European Butterflies and Moths has been carefully described by Mr. Petersen. He adopts Hofman's theory as to the almost total extinction of the Lepidoptera in Europe during the Glacial period. The chief immigration to Europe after that period is, he thinks, Siberian. At first there appeared species which belonged to a cold climate, and which now live in elevated regions; then came forms suited to a milder climate, which established themselves on the north-easterly slopes of the Alps. The most recent addition which our continent has received from Siberia is, according to Mr. Petersen, the present Scandinavian fauna. Scandinavia has obtained a larger number of species than the European plain, because to this last migration were added such as prefer a northern or Alpine climate. As a contribution to the history and composition of the European fauna, by far the most important work ever published is that of Dr. Kobelt, the eminent German conchologist. Whilst the researches into the origin of the Lepidoptera, above described, have been marred by the prevalent prejudice as to the deleterious effects of a glacial climate on the butterflies, the present author boldly works out the problem on independent lines. He shuns theories and speculations almost altogether. His great work, as yet practically unknown, the result of a lifetime of the most painstaking labour, ranks among the most important contributions to zoogeography. I shall have frequent occasion to refer to it throughout these pages. Meanwhile some of his more remarkable conclusions may be mentioned. "Comparing all classes of animals as to their zoogeographical importance, the highest rank must undoubtedly be accorded to the land-snails" (i., p. 7). "The Pleistocene, and with it the land and fresh-water molluscan fauna of the present day has been gradually evolved from the Tertiary one, and its roots can be traced through the Cretaceous to the Jurassic epoch. During the whole of that time no sudden appearance of a new fauna can be demonstrated. Quite slowly, step by step, the Cretaceous is succeeded by the Tertiary fauna, and one after the other of the characteristic palæarctic genera appear--first the fresh-water, then the land forms" (p. 141). "The division of the North Alpine from the South Alpine fauna must be older than the Glacial period; and the present Central European fauna had