VI PKEFACE. 



edition, similar in plan to the first but greatly different in 

 its contents, was almost entirely re-written. This edition 

 has, like the first, been published in parts between the 

 years 1846 and 1855, inclusive. From the high terms in 

 which it has already been alluded to from time to time, 

 in the writings of various active cultivators of different 

 departments of Zoology on the continent, it is obvious 

 that the general estimation of his work will still be such 

 as might be expected in the case of an author of vast 

 erudition, of appropriate tastes, talents and genius, and 

 whose office it has been for nearly thirty years, as Pro- 

 fessor of Zoology in the University of Leyden, to bring 

 the value and import of the new acquisitions of Ana- 

 tomy and Zoology (many of them the result of his own 

 labours) from time to time before his auditors. 



The University of Cambridge, a few years ago, directed 

 in a more marked manner the attention of our students to 

 the Moral and Natural Sciences, by proposing honorary 

 distinctions to those who might excel in certain depart- 

 ments of those sciences respectively; and by requiring 

 proof of satisfactory attention to some one at least of such 

 departments on the part of all candidates for the degree 

 of Bachelor of Arts, who were not aspirants for Mathe- 

 matical honours. Amongst the departments of Natural 

 Science, Comparative Anatomy and Physiology were 

 indicated, with special regard (as is presumed) to Zoology. 

 It thus became a part of my office to place within reach 



