xii PREFACE. 



Unmistakeable processes of Heterogenesis have been 

 watched over and over again by some of the best ob- 

 servers, amongst whom may be named Turpin, Kiltzing, 

 Reissek, Hartig, Gros, Pringsheim, Pineau, Carter, 

 Nicolet, Pouchet, Schaaffhausen, Braxton Hicks, and 

 Trecul. And yet the careful investigations of these 

 well-known naturalists have, upon this particular sub- 

 ject, been either wholly disregarded or publicly repudiated 

 by some leading biologists who not having worked 

 over the same ground themselves rashly trust to 

 their own theoretical convictions, rather than to the 

 positive observations of so many workers. How un- 

 warrantable this conduct has been, almost any compe- 

 tent person however sceptical may learn for himself, 

 if he will but devote two or three months to the careful 

 study of the changes which are apt to take place in the 

 substance of many of the fresh-water Algae, or in those 

 beautiful green animalized organisms known by the 

 name of Euglenae, some of whose marvellous trans- 

 formations were faithfully described more than twenty 

 years ago in the highly valuble but much neglected 

 memoir of Dr. Gros. 



The time is doubtless not far distant when it will be 

 a source of much wonder that those who had already 

 heartily adopted the Evolution philosophy could even 

 in the face of facts long ago known stop short of a 

 belief in the present and continual occurrence of Arche- 

 biosis and Heterogenesis. Do not the very simplest 

 forms of life abound at the present day ? And, would 

 the Evolutionist really have us believe that such forms 

 are direct continuations of an equally structureless matter 



