original text, the arguments by which its conclusions are supported hardly admitting of brief analysis. The most superficial reader will be interested in Mr. Agassiz's account of the mode in which he sought for the natural boundaries of the various divisions, by observing the special point of view in which various eminent naturalists have considered their subject; as, for instance, Audubon, among the biographers of species,—Latreille, among the students of genera,—and Cuvier, at the head of those who have contemplated the higher groups, such as classes and types. The most indifferent reader will be arrested by the opinions boldly promulgated with reference to species.
"The evidence that all animals have originated in large numbers is growing so strong, that the idea that every species existed in the beginning in single pairs may be said to be given up almost entirely by naturalists." "If we are led to admit as the beginning of each species the simultaneous origin of a large number of individuals, if the same species may originate at the same time in different localities, these first representatives of each species, at least, were not connected by sexual derivation; and as this applies equally to any first pair, this fancied test criterion of specific identity must at all events be given up, and with it goes also the pretended real existence of the species, in contradistinction from the mode of existence of genera, families, orders, classes and types; for what really exists are individuals, not species." (pp. 166-167.)
Chapter Third is headed, "Notice of the principal systems of Zoölogy." It is divided into the six following sections: General remarks upon modern systems; Early attempts to classify animals; Period of Linnaeus; Period of Cuvier, and Anatomical systems; Physiophilosophical systems; Embryological systems.
This chapter is invaluable to the general student, as giving him in a single view not only a conspectus, of the most important attempts at classification in Zoölogy, but an examination of the principles involved in each, by the one among all living men most fitted to perform the task. No cultivated person who desires to know anything of Natural Science can pass over this portion of the work without careful study. Those who are not prepared to follow the author through the details of the Second Part will yet consider these volumes as indispensable companions for reference, as containing this brief but comprehensive encyclopedia and commentary, covering the whole philosophical machinery of zoölogical science.
For the first section of this chapter Mr. Agassiz adopts the fundamental divisions (branches) of Cuvier, introducing such changes among the classes and orders as the progress of science demands. The second section gives a short account of the early attempts to classify animals, more particularly of the divisions established by Aristotle. The third section embraces the period of Linnaeus, and gives his classification. The fourth, that of Cuvier, and Anatomical systems, with the classifications of Cuvier, Lamark, De Blainville, Ehrenberg, Burmeister, Owen, Milne-Edwards, Von Siebold and Stannius, Leuckart. The fifth section includes the Physiophilosophical systems, with diagrams of Oken's and Fitzinger's classifications, and a special article for the circular groups of McLeay. The sixth and last section is devoted to Embryological systems, and presents diagrams of the classifications of Von Baer, Van Beneden, Kölliker, and Vogt.
The Second Part of the Monograph introduces us to the consideration of a special subject of Natural History,—the North American Testudinata. Its three chapters treat successively of this order of Reptiles,—of its families,—of its North American genera and species.
The Third Part, contained in the second volume, is entitled, "Embryology of the Turtle." It consists of two chapters: "Development of the Egg, from
