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 polypidoms or 
corals which, by their continual growth, thefr 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 an4 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 
