364 Mr. H. J. Carter on some West-Indian 



ence to the former of their specimens, therefore, I cannot help 

 identifying it with our specimen from Puerto Cabello, and 

 the latter with that from the island of St. Vincent ; for both 

 kinds of pores exist on the surface of the latter. Thus Dr. 

 Bowerbank's G. tubcrcidosa and G. tuniulosa appear to me to 

 be the same as Lamarck's G. r/ihbewsa, which also came from 

 the West Indies. 



Now I have just boiled out in nitric acid fragments of both 

 our specimens, viz. that from Puerto Cabello and that from 

 St. Vincent. But for the spiculation generally of the latter 

 being a little smaller, the two are identical ; and yet the 

 surface of the former is covered with pin-holes regularly and 

 quincuncially arranged in a thick crust of siliceous balls, &c., 

 while the latter is for the most part covered by a dermal re- 

 ticulation in which the interstices are cribbled with pore-holes 

 in a thin one. 



This discrepancy I will now endeavour to explain. It may 

 be remembered, 1st, that in many sponges, especially among 

 the Holorhaphidota (ex. gr. Ilalichondria panicea^ Johnst., 

 Esperia)^ the pores are situated in plurality in the delicate 

 films of dermal sarcode which tympanize the interstices of the 

 skeletal reticulation, thus rendered cribriform ; 2ndly, that in 

 the Psammouemata, where the dermal sarcode is thicker and 

 the interstices (that is, the polygonal divisions on the surface) 

 much larger, the tympanizing sarcode is again divided by a 

 minute subreticulation of soft colourless fibre, which appears 

 in relief on the surface of the polygonal divisions respectively, 

 and presents one or more pores in each of its interstices ; 3rdly, 

 that in many Ilircinice this reticulation becomes still more 

 evident by the addition of minute microscopic objects (sand- 

 grains, fragments of sponge- spicules, &c.), which give it a 

 strikingly beautiful lace-like appearance, especially from its 

 Avhiteness when dry ; 4thly, that this addition of foreign objects 

 often goes on to such an extent as to thicken the lines of the 

 reticulation into a continuous incrustation, leaving only the 

 openings of the pores. 



Now we have only to apply this to Geodia, in which the 

 siliceous balls and their accompanying minute stcllates repre- 

 sent the " minute foreign objects," to understand how, in the 

 specimen of G. gibherosa from the island of St. Vincent, we 

 have a plurality of pores in the interstices, and in that from 

 Puerto Cabello single ones, like pin-holes, in the thickened 

 crust. Indeed, as before stated, the two conditions exist 

 together in the specimen from St. V^incent, and tiierefore 

 prove that these difierences only depend on degree of deve- 

 lopment. 



