FORM OF A SPONGE. .237 



mass, sending forth from one side several tubes, which 

 divide or branch into others. The former portion lies 

 adhering to the face of the sea-weed, but most of the 

 tubes project from the edge of the frond. The longest 

 tube is about J inch in length, and -^ inch in greatest 

 diameter. The tubes terminate with plain transverse 

 orifices, without any thickening : in one the margin 

 is slightly expanded, but this is evidently accidental. 

 The spiculse project from the edge their points in brist- 

 ling array, as they do from the whole surface; and if 

 it were an object of large size, one would say it was a 

 formidable affair to take hold of with ungloved hands. 



I watched carefully for any trace of vortex or cur- 

 rent ; but the particles and floating atoms in the 

 vicinity of the apertures were perfectly still ; and I 

 could not detect the least appearance of motion in the 

 water. If there be any circulation, as Dr. Grant has 

 satisfactorily shown to exist in the genus, it is pro- 

 bably periodical. 



The accompanying figures may assist you to form 

 a notion of the general appearance of this sponge, 

 and of the peculiar structure or armature which I 

 have described above. Fig. 3, Plate XV., represents 

 the natural size of the entire mass ; Fig. 4 the same 

 considerably magnified, attached to the surface of a 

 piece of the sea-weed frond ; Fig. 5 represents the 

 terminal portion of the largest tube, much more 

 highly magnified, with the spiculse, and the granular 

 surface beneath. The colour is dull pellucid white. 

 The characters of the species appear to identify it with 

 the Gra?itia hotryoides of naturalists, a sponge said 

 to be rare in the south of England. 



