Book Description

Excerpt from Papers, Vol. 18: From the Department of Marine Biology of the Carnegie Institution of Washington In 1912, at Montego Bay, Jamaica, I obtained material and began the study of straight-fertilized eggs of Cidaris tribuloides Lamarck, of Cidaris eggs fertilized with the sperms of Lytechinus (Toxopneustes) variegatus, of Cidaris eggs fertilized with the sperms of Tripneustes (Hipponoe) esculenta, and of Cidaris eggs caused to develop parthenogenetically. A brief account of some of the facts determined appeared in Publication No. 182 of the Carnegie Institution of Washington. The present paper includes my completed observations. Nature and Systematic Position of the Material. The nature and systematic position of the forms used demand more than passing notice. Cidaris represents the lower extreme of a series extending from little specialized to highly specialized Echinoids; Lytechinus and Tripneustes represent the upper extreme. Jackson (1912) has shown that the Cidaroida are primitive, extending from the Lower Carboniferous to Recent times. He says: "The most primitive type of Echini, I believe emphatically, is Bothriocidaris [p. 208]. ... The order Cidaroida is placed as derived directly from the Bothriocidaroida without known intermediate forms. The Cidaridæ, as regards the structure of the young and adult, are the least removed from Bothriocidaris of any known echinoid, living or fossil" [p. 211]. Lytechinus and Tripneustes are members of the order Centrechinoida (Triassic to Recent), of the suborder Camarodonta, and of the family Echinidse (Cretaceous to Recent). Again quoting from Jackson (p. 210): "The sub-order Camarodonta may be considered the most specialized of modern regular Echini on the basis of the lantern, and also in various genera by the sculptured test, the degree of specialization of the ambulacrum, peristome, perignathic girdle, or the elliptical form through a sidewise axis." In discussing the lantern, Jackson says (p. 187) that "Tripneustes represents the most complex structure known in the Centrechinoida. 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.