AUTHOR'S PREFACE 



TO THE SECOND EDITION. 



THE friendly reception which the " Text-book of the Embryology 

 of Man and Mammals " has found, is an indication of the increased 

 interest which this branch of Morphology now meets with. 



Even more than a year ago, after the first part of the text -book 

 appeared and while the second part was in the press, the necessity of 

 preparing a second edition became evident. 



In this edition fundamental changes have not been undertaken ; 

 the text has, however, undergone an expansion in some places, owing 

 to the attention given to several works which have recently appeared. 

 This has been the case with the section on the first developmental 

 processes of the egg (WEISMANN, BLOCHMANN) ; that on the origin of 

 the vascular system (RABL, RUCKERT) ; that on the development of 

 the foetal membranes (DuvAL, OSBORN) ; and that on the human 

 placenta (KASTSCHENKO, WALDEYER, HUGE). 



As the second part of the text-book has just appeared, it has been 

 possible to incorporate it in the second edition without alteration. 



It has, furthermore, seemed to me expedient in the second edition 

 to distribute at the ends of the several chapters the synopses of the 

 literature, which in the first edition were brought together at the close 

 of the whole work. Finally, there has been added an index of 

 subjects, by which a more rapid orientation concerning the separate 

 topics will be facilitated ; this will increase the usefulness of the 

 work. 



May the book in this form make for itself new friends, not only 

 among students of medicine and the natural sciences, but also with 

 all those who have a fondness for and a, comprehension of studies 

 in natural science, 



OSCAR HERTWIG. 

 JENA, February 1888. 



