Publisher's Synopsis
Excerpt from The Biological Bulletin, 1909, Vol. 16
When the animals are removed from their burrows the aboral end is usually more or less button-shaped or disc-shaped (figs. 1-4) and firmly attached to a bit of shell, a small stone or other solid object. It is, in short, structurally and functionally a foot. In removing the animals from the sand this foot is often lost, since the attenuated region just distal to it is relatively weak. Sometimes, if the foot happens to be attached to some object near the surface - within 5 - 10 cm. - the attenuated region may be completely absent and the animal may possess something the shape of Fig. 10. In some cases, however, the foot is not attached to any solid object; under these conditions it may take the forms shown in Figs. Sand 6 or almost any form intermediate between them. No well defined adhesive surface is developed in these cases, though grains of sand may in some cases adhere to some part of the region. These marked differences, occurring under natural conditions, suggest that the differentiation of a localized adhesive foot is dependent, at least in some degree, upon contact with a solid substratum, a suggestion which is confirmed by the facts cited below. Such forms of the aboral end as those in Figs. 5 and 6 undoubtedly result from the failure of this region to come into contact with a large solid body. The diameter of the disc is scarcely greater than the greatest diameter of the column the tentacles of large individuals, when fully extended may reach a length of 40 mm. 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.
