Excerpt from Smithsonian Contributions to Knowledge, Vol. 35 The new facts and comparisons add to the data for solution of the impor tant problems of the geographical distribution and the origin of the species of crayfish, and they furnish a basis for practical application to the problems of artificial culture and introduction of new kinds of crayfish. 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.