AUTHOK'S PKEFACE. 



"TlOR some time past I have liad an idea of writing 

 -*- a treatise on General Embryogeny ; and in 1855 

 and 1856 I published a series of articles on this 

 subject in the " Revue des Deux Mondes/' with the 

 double object of determining the results of my own 

 researches, and calling the attention of an intelligent 

 but unscientific public to the wondrous phenomena 

 accompanying the development of living beings. 



These articles are here reprinted, together with 

 an account of the progress made since their first 

 appearance. The doctrines and plan remain the 

 same; but, independently of several additions and 

 modifications of detail, I have almost entirely 

 rewritten the chapter on Infusoria, and have added 

 that on Parthenogenesis, the study of which began 

 just at the period of my first publication. 



Its origin will explain the character of the book. 

 In the original articles I avoided being very technical, 



