Excerpt from Arrangement of the Families of Mollusks: Prepared for the Smithsonian Institution It has been found, after due investigation, that the central nervous system offers in its modifications in the Mollusks, as in the Vertebrates, the best criteria of relationship, and on the num ber of ganglia have been based the division thereof into the two primary groups, mollusca vera and molluscoidea; in the former (mollusca vera), there are three Well developed pairs of ganglia - the cerebral, the pedal, and the so-called branchial (or parieto-splanchnic of Huxley) - each pair being united by com missures in the latter (molluscoidea), there is but one well de veloped pair, homologous with the pedal ganglia of the true Mol lusks. Prof. Huxley, that very able biologist who has so much contributed by his clear mind and convincing logic to the education of the younger naturalists of the present day, has well remarked on the impossibility, or at least difficulty not yet sur mounted, of the enunciation of a diagnosis which will combine the two divisions, and distinguish that combination from others. 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.