INTRODUCTION. 9 



full compensation in its perpetual bloom ; for each coral branch is 

 every where covered with its star-shaped animals, the " coral-blos- 



soms." 



Although the external resemblance to objects of the vegetable king- 

 dom is so striking, there is little similarity in actual structure. Each 

 of these flower-animals has a mouth, and a cavity to receive and 

 digest food ; and the appendages that look like petals are organs fitted 

 either for securing their prey or for some other animal function. Some 

 species have actually been fed, and the process of digestion watched 

 by the naturalist. They are not always invisible animalcules, as has 

 been the common impression ; on the contrary, many of the most 

 common varieties are half an inch in diameter, while others are one, 

 two, or three inches, and still others are a foot to eighteen inches. 

 Neither have they "the consistence of jelly," for the texture is usually 

 more like flesh, and the exterior is sometimes quite firm and even 

 leathery. 



2. The growth of coral has been considered one of the mysteries 

 in science, and so few years have elapsed since the facts were first 

 made known, that it remains to the many a mystery still. How the 

 tree of stone grows and spreads its branches what its connexion with 

 the coral polyps which blossom over its surface, and whence the lime 

 that constitutes it, are points which have been but lately explained ; 

 and there is still room for additional and corrected information. In 



earlier publications of Dr. Job Baster, of Zurichsee, in Zealand, exhibiting singular igno- 

 rance of the subject discussed, and inaccuracy in facts, the complete animality of corals 

 has been since admitted without opposition." 



The sponges have often been improperly classed with corals. There is still doubt as 

 to their animality. The latest investigations seem to establish their vegetable nature. b 



a A more extended history of this science in our own language may be found in Johnston's British Zoo- 

 phytes, 8vo,, Edinburgh, 1 838 ; a work distinguished for its literary as well as scientific excellence : 

 also, in French in Blainville's Man. d'Actinologie, 1834. 



b Of recent authors, Grant, Audouin, Milne Edwards, Bowerbank, Dujardin, and Laurent, consider 

 sponges as animal ; while Link, Bhimenbach, Owen, Hogg, and G. Johnston, have inclined to place them 

 in the vegetable kingdom. See Grant, Edinb. Phil. Jour. xiii. xiv. ; Dujardin, Ann. des Sci. Nat. x. 5, 

 2d ser. 1838, in which he endeavours to show, by minute microscopic research, that they are compound 

 infusoria ; Laurent, on the Spongilte, L'Institut, 1840, pp. 223, 231, 240, and the Microscop. Jour. i. 78, 

 who describes the reproductive organs of the supposed animals ; Hogg, on the Spongilla, Linn. Trans, 

 xviii. 390, who sums up the results of his laboured investigations in the following language, "They have 

 no tentacles, no cilia, no mouth, no oesophagus, no stomach or gastric sac, no gizzard, no alimentary 

 canal, no intestine, no anus, no ovaria, no ova, no muscles or muscular fibres, no nerves or ganglia, no 

 irritability or powers of contraction and dilatation, no palpitation, and no sensation whatever. Surely, 

 then, we cannot any longer esteem these natural substances to be individual animals, or even groups of 

 animals, in which not one organ, or a single function or property peculiar to an animal can be detected." 



3 



