OR OSSEOUS SYSTEM. 1 1 



ences according to the species, they afford useful characters 

 for the distinction of these animals. They are deciduous 

 parts of the skeleton as they fall off after the matured gem- 

 mules have escaped from their interior. These gemmules 

 are seen in little ciliated capsules at m m, and the polypi are 

 seen in the same figure extended in various attitudes from 

 the cells, in search of animalcules as food. The skeleton of 

 these vaginiform zoophytes often presents a jointed appear- 

 ance on the stem or branches, as seen in the campanularia 

 at/"; these consist of circular indentations of the surface 

 which do not pass through the interior of the body where 

 they would interrupt the circulation of the nutritious fluid 

 which passes through the fleshy substance in all parts of the 

 body. They allow of a certain degree of flexibility at the 

 most suitable parts of the skeleton, and in some of the horny 

 cellar'KB they are connected with the deciduous character of 

 the branches. In the gorgonia, and some other cortical 

 zoophytes, there is an exterior fleshy substance in the living 

 state which covers all parts of the horny skeleton. This 

 fleshy exterior crust is indeed the animal, which forms by 

 the deposition of successive layers the whole of the flexible 

 branched, horny, and solid internal skeleton. If we make a 

 transverse section of a thick portion of the gorgonia, or 

 antipathes, we can easily perceive the concentric layers of 

 which it is composed ; and by peeling off the cortical fleshy 

 mass from the exterior, and placing this living flesh in the 

 sea, we find it to secret a new internal horny axis for itself. 

 The polypi, which are always and necessarily continuations 

 of the fleshy substance of zoophytes, are developed from this 

 thick fleshy crust in the cortical kinds, and hence we do not 

 see any appearance of cells on the central horny axis in 

 these animals, after the flesh has been removed. 



In the calcareous zoophytes the solid mass forming the 

 skeleton is composed chiefly of the carbonate of lime, with a 

 little of the phosphate, and the same condensed glutinous 

 matter which forms the entire skeleton in the keratophytes, 

 is diffused through the whole of the calcareous mass in the 

 more solid lithophytes, where it serves to aglutinate the 

 earthy particles, and to give solidity and tenacity to the en- 

 tire mass. The calcareous skeletons of lithophytes are for 

 the most part internal, massive, and consisting of a single 

 piece. In madrepores, and many similar forms, the thin 



