PREFACE, 



This work may very properly be considered as a supple- 

 ment to my History of British Zoophytes. From ray cor- 

 respondents I learned that such a work was expected from 

 me, and I was the more easily induced to undertake it from 

 a belief that no other naturalist was likely to devote his 

 time to illustrate a comparatively limited and isolated class 

 of organized beings, obscure in character, and possessed of 

 less interest than attaches to almost every other. The 

 class may be said to occupy at present a piece of debateable 

 land, lying between the confines of the two organic king- 

 doms, — too poor and barren to be an object of contest with 

 the subjects of either, and'readily relinquished to the occu- 

 pation of any eccentric borderer who may find his pleasure 

 in cultivating an intimacy with its rude tenantry. This is 

 not an easy task, for there is so much that is common to 

 them, and each adapts itself so readily to circumstances 

 and assumes a new mask, that it requires a tact, to be 

 gained only by some experience, to recognize them under 

 their guises ; while we labour, perhaps in vain, to devise 

 phrases which shall aptly pourtray to others the charac- 

 teristics of objects that have no fixed shape, and whose 

 distinctive peculiarities almost cheat the eye. 



