244 PLATE LXXVIII. 



three dark orange vein-like colourings on the body of 

 the sponge reaching from bottom to top." He further 

 states that there was " one osculum only, and that situ- 

 ated at the apex, smooth, and very slightly raised above 

 the membrane." In the half of the sponge I received 

 for examination there are no indications of the osculum 

 described by Mr. Parfitt. 



The dermal membrane is thin and pellucid, but 

 abundantly covered with sarcode within, in which the 

 tension spicula are in some parts rather sparingly and 

 evenly dispersed, while in other parts they are more 

 abundant, and frequently loosely fasciculated. The 

 rete of the skeleton is stout, the fibres frequently anas- 

 tomising, forming elongated interstices, on the mem- 

 branes of which the tension spicula are rather abun- 

 dantly and irregularly dispersed. 



The gemmules in this specimen form a very striking 

 character. They are membranous like those of other 

 species of Desraacidon, but they are strikingly different 

 in their size and general appearance from those in 

 either D. Jeffrey sii or D. pannosus. When fully deve- 

 loped they appear pellucid at their margins, while their 

 central portions are completely filled with closely- 

 packed, small, transparent, globular molecules. The 

 gemmules are exceedingly abundant, and in some parts 

 so much so as to completely obscure the tissues beneath 

 them. They vary greatly in size. One of the largest 

 and best developed measured -^"B" inch in diameter, 

 while a smaller one did not exceed l - 2 \) Q inch in dia- 

 meter, and a very considerable number of them were 

 still smaller. The globular molecules within the 

 largest one measured were 2 $- 7 8 inch in diameter. 

 When present the gemmules will always form a striking 

 specific character, but the species can never be con- 

 founded with any other known British Desmacidon, as 

 it is the only one which has a skeleton constructed of 

 fusiformi- cylindrical spicula, and a further character is 

 the total absence of any other forms of spicula than 

 those of the skeleton. 



