iv. PREFACE. 



The original papers in the Annals of Natural History have 

 also largely yielded materials. In all cases I have been 

 careful to insert the authorities ; and I hope that those 

 who may hereafter quote from this volume will be 

 equally just. 



The aim has been to form as complete a manual as the 

 present state of knowledge will admit ; and I believe that 

 it will be found useful, both to the Natiu'alist and to the 

 Microscopic Observer. 



Canonbury Lane, 



LONDON, 



24a June, 1852. 



