BRITISH SPONGIADjE. 241 



to the first one. The base of Mrs. Griffith's sponge has 

 been destroyed, but that of Dr. Clarke's is smooth and 

 rounded, and has several fragments of Sertularia projecting 

 from it, and these Zoophytes are continued through its 

 whole length, and are seen projecting from the terminations 

 of several of its branches. A small Buccinum is partially 

 imbedded in the basal portion of the sponge, but its true 

 habit appears to be parasitic, surrounding Zoophytes or 

 other branching bodies. Both specimens are inelegant and 

 distorted in form. 



The diameter of some of the largest of the oscula is 

 about the tenth part of an inch, but the greater number 

 are very much smaller in size. The pores are not visible 

 without the aid of an inch lens ; they are very numerous, 

 and are equally dispersed over the surface of the sponge. 



The dermal membrane is in fine preservation in Dr. 

 Clarke's specimen. It is furnished with a network formed 

 of bundles of spicula which are frequently continuous in 

 curved lines over the breadth of five or six of the areas ; 

 they cross each other at various angles, and, as several of 

 these elongate bundles are frequently coincident in their 

 direction, there is an approach to a symmetrical arrange- 

 ment in the network that is very remarkable and charac- 

 teristic. The acerate spicula of the dermal network are 

 slender and short in comparison with those of the other 

 parts of the sponge. 



The acerate spicula of the skeleton are short and stout, 

 while the acuate ones are larger and more slender in their 

 proportions ; the two forms are mingled indiscriminately 

 in the fasciculi of the skeleton, but the acerate one is the 

 most numerous. The tension spicula of the interstitial 

 membranes are of the same form as those of the skeleton, 

 but are more elongate and slender in their proportions ; 

 they are not numerous, and the acuate form prevails in 

 number. 



10 



