The Effects of Inbreeding and Crossbreeding Upon Development, Vol. 207

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Excerpt from The Effects of Inbreeding and Crossbreeding Upon Development, Vol. 207: September, 1918 From the knowledge of alternate inheritance it is possible to ascribe, very definitely and surely, certain of the results of in breeding to the segregation and isolation of hereditary factors which results were formerly thought to be due solely to inbreeding as a cause in itself. Certain pathological, abnormal or otherwise undesirable conditions occurring more frequently in animals and plants produced by matings between nearly related individuals were formerly attributed to inbreeding as the cause, and it was thought that inbreeding must always show such undesirable results. It is now known that many of these pathological and abnormal conditions resulting from inbreeding do not owe their origin to that process, but are due solely to the segregation, into a pure state of the hereditary factors causing the anomalies which factors were present in the organisms previous to their being inbred. Inbreeding, then, has nothing to do with the origin of the undesirable characters under consideration but merely brings them into visible expression, and whether or not they appear depends upon their presence originally in the stock before inbreeding takes place. There still remains a Conviction, however, that all the manifestations attending inbreeding and the converse effects of cross breeding cannot be accounted for solely on the basis of the operation of definable, hereditary factors, but that there is a stimulating effect resulting from crossing, which is lost by inbreeding, and that this stimulation differs somewhat from the expression of hereditary factors which can be transferred and fixed in different organisms. This stimulation is supposed to be of a physiological nature appearing when dis similar germ-plasms are united, and disappearing as the germinal heterogeneity disappears in subsequent recombinations. 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.