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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 'Praeformation
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


Inquiry into the problems of heredity is beset with many difficulties, of
which not the least is the temptation to argue about the possible, or the
probable, rather than to keep in the lines of observation. Setting out from
a laborious and beautiful series of investigations into the anatomy of the
Hydromedusae, Weismann came to think that the organic material from which
the sexual cells of these animals arose was not the common protoplasm of
their tissues, but a peculiar plasm, distinct in its nature and
possibilities. In the course of several years, Weismann not only continued
his own investigations in the many directions that his conception
suggested, but made abundant use of that new knowledge of the nature and
properties of cells which has been the feature of the microscopy of the
last decade. His theory of the germplasm gradually grew, undergoing many
alterations, so that even in its present form he regards it as tentative.
Neglecting the numerous modifications and accessory hypotheses by which he
has sought to adapt the theory to the phantasmagorial complexity of organic
nature, the main outline of the theory is as follows: A living being takes
its individual origin only where there is separated from the stock of the
parent a little piece of the peculiar reproductive plasm, the so-called
germplasm. In sexless reproduction one parent is enough; in sexual
reproduction equal masses of germplasm from each parent combine to form the
new individual. The germplasm resides in the nucleus of cells, and Weismann
identifies it with the nuclear material which microscopists have named
chromatin, on account of the avidity with which it absorbs