ELEMENTARY INSTRUCTION IN PRACTICAL BIOLOGY BY T. H. HUXLEY, LL.D., F.R.S.,. ASSISTED BY H. N. MARTIN, M.A., M.D., D. Sc., F.R.S. REVISED EDITION EXTENDED AND EDITED BY G. B. HOWES, ASSISTANT PROFESSOR OF ZOOLOGY, NORMAL SCHOOL OF SCIENCE AND D. H. SCOTT, M.A., PH. D., ASSISTANT PROFESSOR OF BOTANY, NORMAL SCHOOL OF SCIENCE WITH A PREFACE BY London: MACMILLAN AND CO. AND NEW YORK. [All Rights reserved.] 623346 First Printed 1875. Printe te and nd Stereotyped 1876. Reprinted March and July 1877, February and December 1879, 1881, 1882, 1883, 1885, March, September, December, 1886, 1887. Revised and extended edition, 1888. Reprinted 1889. PREFACE TO THE REVISED EDITION. THE first edition of the Course of Practical Instruction in Elementary Biology appeared twelve years ago, and the motives which led to its publication are fully explained in the original preface, which is subjoined. The present edition has been carefully revised and, where necessary, enlarged by my colleagues Mr Howes and Dr Scott, assistant Professors in Zoology and Botany in the Normal School of Science and Royal School of Mines, and such additions and improvements are entirely their work. But besides these changes, the reader who compares the two editions will observe that the order in which the subjects are presented is completely changed. In the first edition the lowest forms of life were first dealt with; the series of plants followed in ascending order; and then the series of animals, from the Bell animalcule upwards to the Frog. No doubt there is much to be said for the principle of this arrangement, which leads the student from the study of simple to that of complex phenomena; but the experience of the Lecture-room and the Laboratory taught me that |