7fiR 



THE HALICHONDPJA. 



IJS T the genus Grantia, which is well known to marine zoologists as having furnished 

 valuable information respecting the nutriment and reproduction of the Sponges, no horny 

 network can be found, but its place is supplied by the singular form of the spiculse, which 

 are composed of three long-pointed spines arranged so as to form a star of three rays. 

 These rays, on account of their shape, form an entangled mass, and answer the purpose 

 of the ordinary horny framework. The new species shown in the illustration inhabits the 

 East Indies. 



There are several British species of the genus Grantia. Some of them are hollow, 

 and stand out with tolerable boldness from the objects on which they are set, while others 

 are always found as whitish incrustations upon stones and other massive substances. 

 Their structure is tolerably firm, and, on account of the absence of the horny framework, 

 is not so elastic as are the generality of the Sponge tribe ; and the texture is very close, 

 but still porous. With a microscope of tolerably high power, magnifying from two to 

 three hundred diameters, the layer of spiculse can be readily made out, interlacing with 



Haltcliondria paimata. 



each other in wonderful profusion, and so completely intermixed that a single spicula is 

 scarcely ever separable from the general mass. 



The shape of the species belonging to this genus is extremely variable, but in all the 

 structure is remarkably simple, the wall being extremely thin, so that the ramifying canals 

 are not needed, and the water is merely absorbed through the minute pores of the wall 

 and expelled through the large orifice which forms the mouth of the sac. If the spiculse 

 of this or other Sponges be wanted in a separate state, the animal matter can be removed 

 by heat ; but a better, though slower process, is to immerse the specimen in strong nitric 

 acid or liquor potassse, according to the flinty or chalky nature of the spicules. When 

 separated they may be mounted in two ways, namely, as dry and opaque objects, or in 

 Canada balsam. 



WE must now briefly examine a rather important genus of Sponges, which has many 

 representatives in the British seas. It is a very extensive genus, and its members are 

 variously shaped, all, however, agreeing in those salient points on which the group has 

 been founded. They are all spongy, elastic, not slimy, and with a very porous surface. 



