SPONGES. 27 



substance which covers it, so, in its turn, it is supported 

 by a branched and interlaced crystalline network of flinty 

 stars and needles, which make the framing of the channels 

 and passages composing its mass. 



The living masses present various colours to the eye. 

 Some, such as Cliona, which lines the inside of some shells, 

 are of a bright yellow colour ; others, such as Halichondria 

 sanguinea, are of a brilliant crimson hue. 



Grantia botryoides. 



An extremely minute Sponge, consisting of branching 

 tubes, has been carefully examined under a lens by Mr. 

 Gosse, who thus describes what he saw : — '' I immediately 

 transferred it to a glass cell, and applied it to the stage of a 

 compound microscope, with a power of 220 diameters. To 

 my astonishment, a mass of starry crystals met my view, 

 entangled among each other almost as thick as they could 

 lie, by scores, nay by hundreds. Tor a moment the eye 

 was bewildered by the multitude of slender needle-hke points 

 crossing and recrossing in every possible direction ; but 

 soon the curious spectacle began to take some kind of order, 

 the crystals were seen to be all of one form, though varying 

 considerably in length and thickness ; they are three-rayed 



