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THE BIOLOGICAL PROBLEM 



OF TO-DAY 



PREFORMATION OR EPIGENESIS? 

 THE BASIS OF A THEORY OF ORGANIC 



DEVELOPMENT 



RlC-iUfcC C 



# I E 



. 



BY 



PROFESSOR DR. OSCAR HERTWIG 



DIRECTOR OF THE SECOND ANATOMICAL INSTITUTE OF THE UNIVERSITY OF BERLIN 



ut^oriseb translation 



BY 



P. CHALMERS MITCHELL, M.A. 



WITH AN INTRODUCTION BY THE TRANSLATOR 

 AND A GLOSSARY OF THE TECHNICAL TERMS 



'Cr 



THE MACMILLAN CO. 

 NEW YORK 



