10 



ORGANS OF SUPPORT, 



the more distinct forms of keratophytes. In the horny 

 species of zoophytes the skeleton sometimes forms a tubular 

 external sheath enveloping the fleshy substance throughout 

 all the ramifications of the body, as in all the sertularia, 

 plumularice, antennular'uR* and many other soft, flexible, and 

 ramified forms. The horny skeleton is sometimes formed 

 by the deposition of successive layers within the fleshy 

 substance of the animal, as in the gorgonia and antipathes. 

 We have an example of an 

 external, tubular, horny 

 skeleton in the common 

 campanularia dichotoma, 

 Fig. 5, where we observe it 

 enveloping as a sheath the 

 fleshy substance which 

 occupies the centre of all 

 the divisions of the root, 

 the stem, and the branch- 

 es. The exterior horny 

 sheath which is exuded 

 upon the surface of the 

 flesh is seen at a, and this 

 sheath expands at the 

 extremities of all the 

 branches to form cells, b, 

 for the lodgment of polypi 

 e, i. The base of attach- 

 ment, spread out and ram- 

 ified like a root, exhibits 

 the same fleshy interior, 

 and the horny covering 

 extended over all its divisions at c. A magnified view of a 

 small portion of a branch is represented at Fig. 5. 2, which 

 shows the fleshy granular or cellular substance f in the centre, 

 surrounded by the tough, elastic, amber coloured skeleton 

 exuded upon its surface *. In the axillae of many of the 

 branches we observe large vesicles, 1 1, for the protection and 

 development of the embryo. These vesicles in the vagini- 

 form keratophytes are composed of the same firm pellucid 

 substance as the rest of the skeleton ; and from^the con- 

 stancy of their forms in the same animal, and their differ- 



