114 ACCOUNT OF BRITISH SPONGES* 



33. Fragtlis, Fragile, friable, coarsely reticu- 

 lated ; the fibres rugose as if covered with 

 minute sand. 



Plate xiv. fig. I, 2. 



The above specific characters are sufficient to 

 distinguish it from fruticosa, with which it might 

 easily be confounded by a cursory observer. The 

 first obvious distinction to the naked eye, is a 

 slightly frosted appearance, and the colour more 

 usually brown : upon handling, the fibres readily 

 break, and a slight friction between the finger and 

 thumb, reduces it to powder like sand ; but this 

 arenaceous appearance is found, by the assistance 

 of the microscope, to be a tenacious vesicular 

 substance, possessing in some points of view, 

 (when examined under the condensed rays of the 

 sun, or a lamp,) a micaceous lustre. 



A single specimen of this sponge in my cabinet, 

 was originally collected for Jruticosa, and the dis- 

 tinction was not immediately discovered. 



Coast of Devon. 



^4. Parasitica. Texture coarse ; form indefi- 

 nite, determined by the body on which it 

 creeps. 



Frequent on Sertulariae, sometimes following 

 the course of the branches individually, which it 

 envelopes ; at other times spreading laterally, and 

 uniting the branches together, becoming an un- 

 formed mass : the texture is rather coarse, and the 



