PREFACE. 



THE following Essays are, by the kind permission of 

 the Editor, reproduced from KNOWLEDGE, with some 

 emendations, and a few additional illustrations. 



They are intended to illustrate in a popular manner 

 a few of the various modes in which animals espe- 

 cially vertebrates are adapted to similar conditions 

 of existence ; and also to demonstrate some of the 

 more remarkable types of structure obtaining among 

 the higher vertebrates. It will be found that while 

 some of the Essays form a continuous series, others 

 are totally unconnected with those to which they 

 stand in juxtaposition. While living forms are by no 

 means neglected, especial attention is concentrated on 

 the less known, strange, and often gigantic creatures 

 which have now passed away for ever, and are re- 

 vealed to us it may be but obscurely only by their 

 dry bones. 



The series has, the author flatters himself, met with 

 a favourable reception in its original form ; and he 

 trusts that it may obtain at least equal approval in 

 its present guise. 



