50 GENERAL HISTORY OF 



Animalcula Infusoria Fluviatilia et Marina, appeared in 

 the year 1786. On this arrangement is founded my 

 Natural History of Animalcules, prepared in 1832 ; between 

 these two periods the additions to this branch of natural 

 history, from actual observation, was not very great; 

 indeed, until the latter work appeared, this subject could 

 not be said to have assumed a definite character, and was 

 unknown to the Enghsh reader. 



The laborious and long-continued observations of Dr. 

 Ehrenberg, in Germany, have enabled him, after several 

 revisions and amendments, to present us with a classifica- 

 tion which, in my opinion, will remain as long our 

 standard, on this subject, as that of Miiller's has been. 

 It is curious, however, to observe, that in all the publica- 

 tions, up to the present day (in England at least), profess- 

 ing to give an account of Dr. E.'s classification, they 

 have taken it from his older and I may say abandoned 

 systems. 



Dr. Ehrenberg, in his great work entitled Die Infusions- 

 thierchen, has not devoted much space in defining the term 

 Infusoria, or in giving a general view of the subject ; but 

 he commences almost immediately with the class Poly- 

 gastrica; hence the Second Part of this work will give the 

 reader some idea of the general arrangement of that splen- 

 did work ; though the design of the two differing, namely, 

 the latter being a work of reference, this a manual, many 

 alterations, omissions and additions have been made; and 

 hence it will be ahke unjust to that distinguished natu- 

 ralist, as to myself, to consider the one a mere abstract of 

 the other. 



Should the reader possess a copy of the Natural Histonj 



