SPONGES. 5 



Sponges Nos. lG-20 were composed mainly of organic matter, anil only loss on ignition 

 was determined. The figures showing this loss are as follows: 



^ I'er cent. 



16. EtcspoTigin nfficiiialvi 96.94 



17. Hippospongia equiva 96. 9§ 



18. Hipposponijia agaricina Jo.oo 



19. Hippospongia caniculala 94.71, 



20. Aplysina hirs^ita 93 . 34 



In these sponges the inorganic matter is so small that it may only represent impm-ities, 

 an analysis of which would lie meaningless. Euspongia and Jlippospon^ia are the ordinary bath 

 sponges of commerce. 



In several of the analyses, notably in Nos. 3, 5, 7, 10, and 12, the summation is very low, 

 on account of the presence of soluble salts (sea salt), which were not determined. Analyses 

 1 to 12 represent siliceous sponges, and in Nos. 2 and 6 the siliceous spicules were very conspicuous. 

 No. 1, Eiiplectella, the beautiful "Venus's flower basket," may be taken as the type of these 

 sponges, and the analysis shows that its skeleton is composed of nearly pure opaline silica. 

 Several analyses of siliceous sponge spicules by other chemists lead to similar conclusions. In 

 spicules from unnamed species J. Thoulet - found from 12.88 to 13.18 per cent of water, F. E. 

 Schulze ^ cites an analysis by Maly of spicules from Poliopogon amadou which contained 7.16 per 

 cent, and in seven species of siliceous sponges W. J. SoUas * found water varying from 6.1 to 

 7.34 per cent. In all these sponges the spicules or skeletons are composed of amorphous opaline 

 silica. The other constituents shown in our analyses, except organic matter, which is included 

 in the loss on ignition, are probably but not certainly impurities. To this statement one excep- 

 tion may be made. The phosphoric oxide is perhaps a part of the organisms, which contain it 

 not as such but as phosphorus in some organic compound. This, however, is by no means 

 certam. That nearly all the sponges analyzed contain phosphorus in some form, although in 

 small amounts is clear. 



Analysis No. 13, of SpirioseJla, is very high in organic matter, and its precise character is 

 doubtful, at least so far as the chemical evidence goes. Nos. 14, 15, 21, and 22, however, repre- 

 sent calcareous sponges. Reducing the analyses to standard form, rejecting organic matter, 

 and recalculating to 100 per cent, we have the following figures for their inorganic portions: 



Reduced analyses of calcareous sponges. 



94 



14. 10 

 84.96 



(?) 

 .00 



100. 00 



We can not assign much weight to these analyses, because the specimens analyzed evidently 

 contained impurities— silica and sesquioxides. Even the small amounts of phosphate shown m 

 two of them may be due to the inclosure in the sponges of minute crustaceans, such as copepods. 

 The small percentages of F^O, in the unreduced analyses are much magnified in the reduction. 

 Some of the magnesia also may belong to inclosed sea water, and in this respect analysis No. 14 

 is especially questionable. The presence of magnesia, however, in these sponges is somewhat 



■ Thoulet, I., Compt. Rend., vol. 98, p. 1000, 1S,S4. 

 » Srhiiljc, K. K., Challenger Kept., vol. 21, p. 2S, ISH". 

 < Sollas, W. .1., i(li-m. vol. ii, p. xlviii, l«vS. 



