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SCIENTIFIC LITERATURE.

the evolution of the human intellect. The book as a whole, however, is highly readable, and, with the reserves we have indicated, may be commended to those who are interested in the study of sociological questions.

The Text-Book of Zoölogy[1] of Messrs. T. Jeffery Parker and William A. Haswell was prepared under peculiar, we might well say unique, conditions. Both authors are professors of biology at the antipodes, Professor Parker in the University of Otago, New Zealand, and Professor Haswell in the University of Sydney, New South Wales. They have collaborated while being most of the time twelve hundred miles apart by sea, and the manuscripts, proofs, and drawings of the book have had to traverse half of the circumference of the globe, or to London, in their journeys between the authors on the one hand, and the publishers, printers, artists, and engravers on the other. Though large and comprehensive, the book has been prepared with strict reference to the needs of the beginner, the mode of treatment being such "that no previous knowledge of zoology is assumed, and students of the first and second years should have no more difficulty in following the accounts of the various groups than is incidental to the first study of a complex and unfamiliar subject." Laboratory and museum study is contemplated, and the practice of preceding the study of a given group as a whole by the accurate examination of a suitable member of it is commended. Yet this method of types has its own dangers. "Students are in their way great generalizers, and, unless carefully looked after, are quite sure to take the type for the class, and to consider all arthropods but crayfishes and cockroaches, and all molluscs but mussels and snails, as non-typical." Hence a zoölogy that confines itself largely to types as examples "is certain to be a singularly narrow and barren affair, and to leave the student with the vaguest and most erroneous ideas of the animal kingdom as a whole." The authors, believing that every group which can not be readily and intelligibly described in terms of some other group should be represented in an elementary course of zoölogy by an example, have in the majority of cases described in some detail an example; and in cases where the diversity of organization is very great, two or more examples of every important class. By the time the example has been studied a definition of the class and of its orders will be intelligible, and will serve to show which of the characters already met with are of distinctive importance, and which special to the example itself. To make this part of the teaching more clear, a paragraph giving in more or less of detail the systematic positions of the example, is introduced after the classification. Following the table of classification with its brief definitions, the general account of the group is given, space being allotted to each group, so far as practicable, proportioned to its complexity and range of variation. Following out the plan of deferring the discussion of general principles till the facts with which they are connected have been brought forward, the sections on Distribution, the Philosophy of Zoölogy, and the History of Zoölogy have been placed at the end of the book. But, other considerations being thought more important in those cases, the general account of the structure and physiology of animals has been inserted immediately after the introduction, and the section on Craniate Vertebrata before the


  1. A Text-Book of Zoölogy. By T. Jeffery Parker and William A. Haswell. New York: The Macmillan Company. Pp. 779 and 08a. Price, $9.