Excerpt from Proceedings of the Academy of Natural Sciences of Philadelphia, Vol. 60: 1908 Figs. 1 and 2 were drawn with the aid of a camera lucida and magnified about 72 diameters. Figs. 3 and 4 were drawn with a camera lucida and magnified about 270 times. The succeeding figures were drawn free-hand from living animals with the exception of figs. 7 and 8, which are semi-diagrammatic. They are i natural Size. 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.