PKEFACE TO THE SECOND EDITION. 



rPHE reception accorded to this work has been so 

 favourable as to induce the Publisher to issue 

 a second edition, in which such new matter should 

 be embodied as the progress of Microscopic science 

 might require. He therefore applied to the Author 

 but he found to his regret that the state of Mr. 

 Davies's health was such as to forbid his under- 

 taking the labour. He had, however, collected 

 many valuable notes and memoranda, which he 

 was willing to place at the disposal of any gentle- 

 man who might be selected to edit the work. The 

 Publisher then consulted the present Editor, who, 

 after some hesitation, consented not only to use 

 his best efforts with the ample materials placed at 



