Excerpt from The Cambridge Natural History, Vol. 10 I have to thank my editors for the trouble which they have taken in the revision of the proofs and for many suggestions. To Professor Osborn, of Columbia University, New York, I am indebted for some kind suggestions. My daughter Iris has assisted me in various ways. Finally, I desire to express my indebtedness to l'lr. Dixon and to Mr. M. P. Parker for the care which they have taken in the preparation of the figures which were drawn by them especially for this work. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.