196 ADDITIONS AND CORRECTIONS. 



ter invests each spiculum ; and the spicula are also connected 

 together by an organic membrane filled with minute transpa- 

 rent granules, and probably soft and mucilaginous in a re- 

 cent state.* The spicula are in general long, stout and 

 fusifoiTn, rather acutely pointed at both ends ; and with the 

 larger ones there are intermixed some of more slender pro- 

 portions, and some of those which touch the skin are forked 

 with two or three prongs, to support, as it were, the globules 

 which constitute the crust. This, when dry, is of a chalky -white 

 colom-j with a dusky subvillose surface, dimpled in some places 

 with numerous pores placed pretty closely together, and large 

 enough to be visible with the naked eye. It is scarcely a line 

 in thickness, and is composed of a congeries of innumerable glo- 

 bules prettily arranged and cemented together by an organic mu- 

 cus, so as to form a solid pavement. The little globules are not 

 all of the same size, though mostly so, and, when highly mag- 

 nified, their surface appears minutely reticulated. They are so- 

 lid crystalline balls of silex. 



This description is made from the portion of his specimen 

 which Dr Fleming kindly sent me. The sponge has a close and 

 evident relationship to the " Alclonio primo di Dioscoride" of 

 Donati, (Stor. Nat. Mar. dell' Adriat. Iviii. tav. 8, fig. A, B, C, 

 D, E, F, G,) but in this the spicula are represented as project- 

 ing far beyond the crust. The relationship is not less close 

 to the Geodia tuherosa of Schweigger, (Beobacht. p. 40, pi. iii. 

 fig. 18, 19,) but the imperfection of his description forbids us to 

 pronounce on the sameness of the two. Schweigger even speaks 

 of the fibres or spicula being intermixed with lime, but he was 

 undoubtedly deceived by the white chalkiness of the crust. 



Schweigger's Geodia tuberosa is synonymous with the Geodia 



* " The fleshy matter surrounding the great radiant spicula is a very 

 beautiful structure, highly cellular and abounding in cytoblasts. There 

 is also a beautiful vascular tissue meandering through it in every direc- 

 tion, and in some of these vessels there are molecules similar to those I 

 have described as existing in some parts of the vascular tissue surround- 

 ing the fibre of one of the sponges of commerce. In this same fleshy 

 matter I also observed a few stellate spicula." J. S. Bou-erbank. 



