PREFACE TO THE SECOND EDITION. 
HE 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 
