404 Mr. J, S. Bowerbank on the Spongiadse, 



brane, thickly overspread with minute semi-opake granules : such 

 is its appearance in specimens which have been preserved in spirit 

 immediately on being removed from the sea ; but after having been 

 di'ied, the membrane and its granulated coat is usually fractured 

 in every direction, and then presents an appearance as if the cavity 

 were lined with irregular, minute flocculent masses, or the mem- 

 brane separating from the surface of the canal may be seen repo- 

 sing in it in the form of a contracted tube. Portions of it may 

 also be occasionally seen projecting from the fractured ends of 

 the fibres, especially in the examinations of dried specimens. 



I have been unable to detect any communication between the 

 great central cavity and the outer surface of the fibre, the pro- 

 jecting ends of which are always naturally hermetically sealed. 



I have been favoured by my friend Dr. Veronge with a very 

 beautiful species of this genus which was immersed in spirit im- 

 mediately on being removed from the sea. This specimen is in 

 the form of a cluster of cylindrical tubes about twelve inches in 

 height and two in diameter, the thickness of the tube being about 

 half an inch. 



The whole of the external and internal surface of the sponge 

 is closely covered with a strong investing membrane, and I have 

 observed the remains of a similar tissue upon several other dried 

 species of this genus in my possession. In all the cases the mem- 

 brane was simple in structure, semi-opake, and had the internal 

 surface abundantly furnished with tessellated cellular structure. 



The interstitial fleshy matter of the specimen presented to me 

 by Dr. Veronge exhibits a high degree of organization. When a 

 section was made at right angles to the axis of the sponge, it cut 

 as firmly, and presented as close a texture as a section of the 

 liver of a quadruped does. 



When minute fragments were examined by transmitted light 

 and a microscopic power of 300 linear, it was found to consist of 

 closely compressed tessellated cellular structure, varying some- 

 what in its general aspect in different parts of the specimen, but 

 in the best-defined portions it presented the appearance repre- 

 sented by PI. XIII. fig. 8. 



A few minute vessels were observed in the most transparent 

 portions of this tissue meandering amid the cells, but in other 

 species in which portions of the remains of the interstitial fleshy 

 matter were found, they were observed to exist in a much greater 

 abundance. 



I have been unable to detect more than a few accidental spi- 

 cula in the investing membrane of any of this family, and I be- 

 lieve that they do not naturally exist in any part of any one of 

 the species of this group. 



The Verongice have existed at former periods in great abun- 



