PREFACE. ix 



my entails : the means of their propagation and increase are the 

 first of a series of facts on which a theory of generation must 

 rise ; the existence of vibratile cilia on the surfaces of membranes, 

 which has since been shewn to be so general and influential 

 among animals, was first discovered in their study ; and in them 

 is first detected the traces of a circulation carried on indepen- 

 dently of a heart and vessels. The close adhesion of life to a 

 low organization, — its marvellous capacity of redintegration ; the 

 organic junction of hundreds and thousands of individuals in one 

 body, the possibility of which fiction had scarcely ventured to 

 paint in its vagaries, have all in this class their most remark- 

 able illustrations. On the geologist zoophytology has pe- 

 culiar claims. Its subjects are apparently the first of animals 

 which were called into existence, and from that high date to 

 this time, they have played a part in the earth's mutations, from 

 chaos to the present well ordered scene, greater perhaps than 

 any other class of beings. Separating from the waters of the 

 ocean the calcareous matter held in solution, they reduce it to 

 a solid state ; constructing therewith their varied j)olypidoms or 

 corals which, by their continual growth, their coalescences, their 

 enormous numbers and extent, first roughen the smooth basin 

 of the sea, raise up reefs and ridges that obstruct the hitherto 

 open course of navigation, and become ultimately the founda- 

 tion of islets and islands that remain the " monumental relics" 

 of the puny race. As now the process and change goes on in 

 tropical seas, — so operated it, in the preadamic times, over the 

 waters of the globe, for it is principally from the debris of poly- 

 pous 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 es- 

 timation of others, they sway him little, and lie apart from his 



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

 b 



