vi PREFACE. 



numerous illustrations to this work will form a valuable guide in such 

 cases, and render the descriptions of microscopic animals and plants, of 

 minute structures, tissues, &c, which form the main body of the volume, 

 a real dictionary of objects. At the same time it is not unreasonable to 

 expect that much advantage may be derived from the attention that has 

 been paid to directing observers to subjects and disputed points on which 

 new information is desirable. 



To the lovers of Comparative Anatomy, Physiology, or of the Natural 

 History of the microscopic members of the Animal and Vegetable King- 

 doms, the Authors have endeavoured to furnish, without departing from 

 the principal purpose of the work, something more than a mere descriptive 

 catalogue of objects, and the means of examining them. Numerous 

 articles on various subjects have been written with a view to enable 

 readers, by the help of the system adopted, and references printed in 

 small capitals, to acquire a general knowledge of particular departments 

 of science. Thus, taking a departure from the article Animal Kingdom 

 or Vegetable Kingdom, the reader may proceed to the Classes and Orders 

 there enumerated ; under the latter will be found a general description of 

 these (where the microscope is much required in their investigation), fol- 

 lowed by a reference to the Genera, under which is given more or less 

 extensive information on the Species, according to the state of knowledge, 

 or as the subject has seemed to require. Proceeding from the article 

 Tissues, in like manner, the details may be gradually collected by tracing 

 them through the subdivisions by means of the references. Many other 

 general articles are given, with such headings as the names of well-known 

 organs or substances, of vital or other phenomena, &c., under which could 

 be conveniently collected references to a variety of miscellaneous informa- 

 tion scattered through the alphabetical arrangement. Those who use the 

 volume in this way will probably derive the greatest amount of advantage 

 from it j they will, it is true, most clearly perceive the deficiencies inevi- 

 table in a great measure to a work having such an extensive field, and at 

 the same time so limited a compass. 



The results of a large amount of independent observation have been 

 consigned to these pages; and, as the bibliographical references show, 

 recourse has been had, as far as possible, to original sources for trustworthy 

 and reliable information published at home and abroad. In connexion 

 with this, some account may be given of the illustrations. In the Plates, 

 a large number of the figures are original, drawn from the objects either 

 by the authors or by Mr. Tuffen West ; in many cases, however, figures of 

 species have been designedly taken from original plates, especially when 

 the verbal characters were doubtful. The Authors feel bound to express 

 their thanks to Mr. West for the manner in which he has applied his well- 

 known skill and accuracy to those engravings which were entrusted to 

 him : many of them, indeed, appear at first sight somewhat crowded and 

 on a small scale ; but they will be found in most cases to display very 

 clearly the parts of objects on which systematic or structural characters 

 depend, the chief design of all the illustrations of this work. With regard 



