VI PREFACE. 



fully grasp after he has attained a knowledge of the 

 leading modifications of structure exhibited in the 

 Animal Kingdom. The Author has only to add 

 that the first part of the work (on the Invertebrate 

 Animals) has been carefully revised, and, as far as 

 possible, brought up to the present level of the Science ; 

 whilst the illustrations, with very few exceptions, have 

 been drawn upon the wood by himself. 



EDINBURGH, December i, 1870. 



