X PREFACE. 



specially aided in treating of the Applications of the instrument, 

 he would especially name Mr. Quekett's valuable Lectures on 

 Histology (Vegetable and Animal), Mr. Ralfs's beautiful Mono- 

 graph on the British Desmidiese, Prof. W. Smith's on the Diato- 

 macese (which will, when complete, be quite worthy to take 

 rank with the preceding), and the Micrographic Dictionary. 



All the Illustrations have been drawn by Mr. W. Bagg, and 

 have been engraved under his superintendence ; and the Author 

 ventures to affirm, that for fidelity as well as for beauty of 

 execution, they will bear comparison with any Microscopic de- 

 lineations yet executed on wood. A large proportion of the 

 subjects are original ; the sources of all that are not so, are spe- 

 cified in the list (p. xvii). 



The Author feels that some apology is due for the long delay 

 which has attended the appearance of this work. When it was 

 first announced as forthcoming, his full intention was to apply 

 himself immediately to its production ; but the unexpected de- 

 mand for new editions of his two large Treatises on Physiology, 

 required that the whole of his disposable time and attention 

 should be given up during two years to carrying these through 

 the press. When he at last found himself free to apply himself 

 to the "Microscope," he fully expected that the forward state of 

 his preparations would enable him to complete it by October, 

 1855. But in this expectation he has been disappointed by the 

 occurrence of two severe attacks of indisposition, which com- 

 pelled him for a time to suspend all mental exertion, and have 

 rendered it necessary for him carefully to abstain from overtask- 

 ing himself; so that he feels assured that those who have kindly 

 waited for the appearance of this volume, will not, when ac- 

 quainted with these circumstances, blame him for a delay, the 

 causes of which have lain so completely beyond his control. 



UNIVERSITY HALL, LONDON, 

 Feb. 9, 1856. 



