PREFATORY NOTE TO VOLUME SECOND. 



Since the publication of the First Volume of this Work, the 

 researches of Naturalists and Microscopists have considerably 

 extended the number of British species belonging to the genera 

 therein described. I have appended a list of these to the pre- 

 sent volume ; but I feel satisfied that much yet remains to be 

 done before this field of inquiry can be regarded as sufficiently 

 explored. 



Under these circumstances, I have thought it better not to 

 detain the publication of this volume for the engraving of the 

 additional forms already discovered in the British Isles, as this 

 delay would probably render nugatory the attempt to give the 

 work the character of a complete monograph ; but to look for- 

 ward to an opportunity of preparing a Supplement, bringing 

 down the subject to a more advanced stage of observation and 

 inquiry. 



For the same reason I abstain from indicating the alterations 



in the specific arrangements and synonymy of the First Volume, 



that an acquaintance with new forms and continental specimens 



would seem to justify or require, as each day supplies fresh 



materials for a correct judgment, and enables me to modify or 



confirm with greater certainty the opinions I have already 



recorded. 



The great interest taken in the subject of British Diatomaceae, 



a 2 



