ORGANS OF SUPPORT, 



FIG. II. 



canals. The form of the spicula which belong to several 

 distinct species of poripherous animals are shewn in Fig. 2. 

 at C. D. E. F. G. H. I. K. L. M., each of these forms belong- 

 ing to a distinct animal, and serving to characterize it. The 

 pores are surrounded with groups of spicula disposed in such 

 a manner as to strengthen and protect the parietes of these 

 minute orifices, and to form a delicate net-work over the whole 

 surface of the body, as shewn on a magnified scale at O, 

 and a single pore is shewn at N still more magnified, with its 

 bounding and defending spicula, and a delicate gelatinous 

 net- work, which protects it from the entrance of small foreign 

 particles floating in the water. The silicious spicula are 

 found in some of these animals while they are yet floating 

 gemmules newly detached from the parent mass, and seeking 

 a suitable place to fix and develope. One of these gem- 

 mules is figured at P, highly magnified, and broken to show 

 the spicula already developed in the cellular substance of this 

 minute embryo. Similar silicious spicula occur abundantly 



