iv PREFACE. 



An Introduction has been prefixed to the ' Dictionary/ affording instruc- 

 tions for the selection of a Microscope and the accessory apparatus, explaining 

 the manner of using these, and particularly the precautions requisite with the 

 less perfect, but more economical foreign glasses ; and lastly, entering minutely 

 into what may be called microscopical manipulation and the special education 

 of the eye. 



Many valuable contributions to our knowledge of the structure or 

 functions of microscopic organisms are probably lost, through the inability of 

 microscopic observers to ascertain readily the name and position in Nature of 

 objects which fall under their notice. It is hoped that the very 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 advan- 

 tage 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 Kingdoms, 

 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), followed 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 phsenomena, &c., under which 

 could be conveniently collected references to a variety of miscellaneous infor- 



