Produced by Bryan Ness, Josephine Paolucci and the Online Distributed Proofreading Team at http://www.pgdp.net. (This book was produced from scanned images of public domain material from the Google Print project.) Heinemann's Scientific Handbooks THE BIOLOGICAL PROBLEM OF TO-DAY HERTWIG Heinemann's Scientific Handbooks THE BIOLOGICAL PROBLEM OF TO-DAY _PREFORMATION OR EPIGENESIS? THE BASIS OF A THEORY OF ORGANIC DEVELOPMENT_ BY PROFESSOR DR. OSCAR HERTWIG DIRECTOR OF THE SECOND ANATOMICAL INSTITUTE OF THE UNIVERSITY OF BERLIN Authorized Translation BY P. CHALMERS MITCHELL, M.A. _WITH AN INTRODUCTION BY THE TRANSLATOR AND A GLOSSARY OF THE TECHNICAL TERMS_ LONDON WILLIAM HEINEMANN 1896 [_All rights reserved_] PREFACE Shortly after the appearance of Dr. Oscar Hertwig's treatise 'Präformation oder Epigenese?' I published in _Natural Science_ (1894) a detailed abstract of it. But the momentous issues involved in the problem of heredity, and the great interest excited by Dr. Weismann's theories, make it desirable that a full translation should appear. By the kindness of Dr. Hertwig and his German publisher, this is now possible. I have prefixed an introduction, written for those who are interested in the general problem, but who have little acquaintance with the technical matters on which the argument turns. In the actual translation I have tried no more than to give a faithful rendering of the German. After no little perplexity, I have rendered the German word _Anlage_ as 'rudiment.' It is true, a double meaning has been grafted upon the English word, and it is widely employed to mean an undeveloped structure, without discrimination between incipient and vestigial character. I use it in the etymological sense, as an incipient structure. For the difficult words, _Erbgleich_ and _Erbungleich_, a succession of new terms have been suggested. Here I use for the first term the word 'doubling,' for the second 'differentiating.' P. C. M. TRANSLATOR'S INTRODUCTION