Excerpt from The Sessile Barnacles (Cirripedia) Contained in the Collections of the U. S. National Museum: Including a Monograph of the American Species By the copious illustration of American forms, by large-scale draw ings and photographs, their identification should be easier. Until one has studied barnacles deeply enough to have standards of com parison, even the inimitable descriptions of Darwin are difficult to follow, especially if one is dealing with forms differing somewhat from those described. The appeal to the eye will often relieve the student from uncertainty. Identifying by the pictures may be a primi tive and superficial method, yet such short cuts are permissible in case one merely needs the name of an animal which has been taken as the subject of embryological, ecological, or other non-systematic studies. The student must be warned, however, that many species have parallel mutations, vary in the same way under similar condi tions, so that external form by itself is rarely a reliable criterion. The opercular valves, the details of structure of the plates of the wall, and the structure of the feet are the important characters. 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.