XIV PREFACE. 



mic times, over the waters of the globe, for it is principally 

 from the debris of polypous excretions, that the extensive 

 beds and quarries of chalk and limestone, which are found 

 in every region of the globe, take their original.* But it is 

 to the zoologist that I exclusively address myself in this 

 work, and however considerations like the above may enhance 

 the importance of the subject in the estimation of others, 

 they sway him little, and lie apart from his more immediate 

 objects. He finds his pleasure in the contemplation of their 

 novel forms, in the examination of those characters which 

 distinguish them as species, in the quest of their mutual 

 affinities, their relations and analogies with other beings, 

 the order in which Creative Wisdom may seem to have 

 called them into existence, their habits, economy, and uses ; 

 and in all these things he is ever watchful to find a " moral 

 compliment," that the pursuit to which his taste and consti- 

 tution of mind has led him, may be neither uninfluential nor 

 virtueless on his heart. 



The plates and wood-cuts which illustrate the volume are, 

 with few exceptions, original, engraved from drawings made 

 for it by Mrs. Johnston, who is herself the engraver of four- 

 teen of them. The naturalist who may have attempted 

 similar illustrations will appreciate the labour, perseverance, 

 and skill which has been bestowed upon them, and will not 

 harshly censure any errors of detail which a minute criticism 

 may discover. As I could not have undertaken this history 

 without her assistance, I may crave, from any one who shall 

 find a merit in it, the ascription of that merit to my col- 

 league. 



* See Lamarck's Anim. s. Vert. ii. 10. 



BERWICK-UPON-TWEED, 

 August 15, 1838. 



