1873.] DR. J. S. BOWERBANK ON CEYLONESE SPONGES. 27 



Holdsworth from the 8-fathom part of the Great Pearl-bank at Ceylon. 

 It was immediately immersed in spirit ; and my friend states that it 

 " has not appreciably altered in appearance, shape, or colour since I 

 first took it in my hand. It is the only one of the kind I have seen." 



The regular conical form of this species is very characteristic, as I 

 do not know any other species of the genus, either British or foreign, 

 that has any well-defined form. The surface characters also are 

 unlike those of any other known species. 



The internal structure very closely resembles that of our British 

 species J), fragilis, exhibiting precisely the same mode of increment 

 that I have described in my ' Monograph of British Sponges, 5 vol. i. 

 pp. 78 & 21 1, figs. 270-272, as prevailing in that species. The ske- 

 leton-structure is more membranous than fibrous, the latter being; 

 frequently more like thickened membranous edges than true fibres, 

 with the membrane extending between them. Most frequently the 

 membranous extensions are completely covered by a single stratum of 

 particles of sand firmly cemented to them, which are so closely packed 

 as to completely resemble a piece of fine mosaic work ; and no artist 

 could adjust the positions of the large and small pieces of sand with 

 greater precision than that exhibited on the membranes of the sponge. 

 There is something more than the mere adhesion by chance in the 

 attachment of the grains of sand to the membrane. The close and 

 accurate adjustment of the particles to each other, the filling in of 

 all the angles as completely as the most careful workman in mosaics 

 would have adjusted them to each other, plainly indicate something 

 more than a mere dispersion of the grains over the membranous sur- 

 face. We find the fibres projected from the mass of the sponge in 

 search of grains of sand with which to form the artificial skeleton of 

 the animal ; and it is but a step further in the organization possessed 

 by the auimal to imagine that this beautiful arrangement of the par- 

 ticles of sand on the membrane is achieved by the contractile power 

 that we know those tissues to possess. It is well known that they 

 can contract any portion of their own substance, and thus open pores 

 for the imbibition of nutriment, and, if alarmed, again close them so 

 completely that their very position becomes invisible ; and it is but a 

 step further to believe that the same description of voluntary con- 

 tractile power has enabled them so to operate by contractions of the 

 tissue as to bring every molecule of sand cast upon its surface into 

 close conjunction with each other in the complete and beautiful 

 manner that obtains in this sponge, and thus form the exquisite 

 mosaic arrangement that may be seen on its membranes. 



If we are to judge by the amazingly various and beautiful struc- 

 tures exhibited in the sponges, we must certainly credit them with 

 an amount of instinctive power they have hitherto never been ima- 

 gined to possess, and assign them a much higher position amidst the 

 lower animals than they have hitherto been supposed to merit. Oc- 

 casionally there are spots of interstitial membrane unocccupied by 

 grains of sand ; and these were abundantly furnished with lenticular 

 nucleated cells of rather unequal sizes, the nucleus being visible in 

 the largest ones only. 



