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 spiculae project from the edge their points in brist- 

 ling array, as they do from the w^hole surface; and if 

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

 formidable afi'air to take hold of w^ith 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 spiculee, and the granular 

 surface beneath. The colour is dull pellucid w^hite. 

 The characters of the species appear to identify it with 

 the Grantia hotryoides of naturalists, a sponge said 

 to be rare in the south of England. 



