The Journal Of Experimental Zoology Volume 24 PDF Download

Excerpt from The Journal of Experimental Zoology, 1918, Vol. 24 Is there a direct transformation of one type of cell or differentiated part of a cell into another, and if so how is this transformation brought about? What is the nature of the physico-chemical changes which constitute structural regulation in the cell? The following facts derived from a careful study of over 3500 individuals of the ciliate protozoan Bursaria sp. are presented with the hope that they may help to throw light on these questions and possibly point out what is the general nature of the process which brings about dedifferentiation. II. The Normal Process Of Differentiation And Dedifferentiation 1. During cell division In any structurally differentiated cell which does not possess any plane of symmetry it is necessarily true that cell division would result in the formation of dissimilar parts unless some process took place through which the daughter cells became alike. The more striking cases of this kind occur among the more differentiated types of protozoa Wallengren ('01). But even in this group it is difficult to find examples where the process of structural regulation at division can he followed with any degree of ease. Bursaria, a heterotrichous ciliate of fairly common occurrence, is of sufficient size and complexity of organization to permit one to follow with relative clearness the change in structure which occurs during cell division, regeneration and certain othes processes. Figures 1 to 6 inclusive, of plate I, show ventral views of Bursaria in different stages of division. The closure of the gullet and peristome results in a complete disappearance of the membranelles lining the dorsal wall of the gullet (figs. 2 and 3, m), and other structures such as the ciliated ridge or septum (fig. 1, s). 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.