16 



THE INORGANIC CONSTITUENTS OF MARINE INVERTEBRATES. 



Two of these analyses resemble those of corals and mollusks; the third is more like one of 

 an alcyonarian or an echinoderm. In all three the organic matter is very low. Three other 

 partial analyses by Forclibammer '° are on record, which may be compared with these; although 

 only magnesium carbonate was determined. These are — 



Per cent MgCOj. 



Serpula sp. Mediterranean 7. 644 



Serpula triquelra. North Sea 4. 455 



Serpula fdograna -" 1.349 



The tubes of Serpvla are evidently quite variable in composition, at least as regards their 

 magnesian content. 



The tubes formed by Leodice and HyalincBcia, being highly phosphatic, are difficult to 

 interpret chemically. The bases are insufficient to satisfy the acids if the phosphoric oxide is 

 assumed to represent the normal tribasic salts. Phosphorus maj' be present as part of the 

 organic matter, and so, too, may a portion of the sulphm-. Metaphosphates, pyi-ophosphates, 

 and acid orthophosphates are also possibly present, and between these alternatives it is not easy 

 to decide. Acid salts are, however, improbable, for when boiled in water the tubes give faintly 

 alkaline reactions. We prefer, therefore, to leave the reduction of analyses 4, 5, and 6 in abey- 

 ance until moi-e evidence can be obtained. In this direction an analysis of Onuphis tubicola 

 Miiller, by Schmiedeberg,-^ is suggestive. To the organic matter of the tube of Onuphis, "onu- 

 phin," he assigns the formula C24H43NO18, and the tube itself he regards as a complex compound 

 of the composition 



C2,H,3NO,, + CaHPO, + 4MgHP0, + 22H2O. 

 The analyses given by Schmiedeberg are as follows: 



Analyses of Onuphis tubicola. 



In a general way this analysis of Onuphis resembles our analysis of Hyalinoecia, except 

 that the magnesia is much higher and the sulphates, if present, are insignificant in amount. It 

 will be noticed, moreover, that Schmiedeberg assumes the presence of acid phosphates in his 

 interpretation of the data, which, as we have already stated, is improbable. 



None of the analyses of the phosphatic worm tubes can be regarded as wholly satisfactory, 

 but it is clear that these structures add phosphorus to the sediments. If they decay in contact 

 with calcareous sediments, the final product would probably be a tribasic phosphate, and that 

 is as far as we now need to go. 



" Forchhammer, G., Neues Jahrb., 1S52, p. SS4. 



» In a later memoir (Philos. Trans., vol. 15.1, p. 203, 1865) Forchliammer gives the percentage of MgCOs in Serpula filo^ana as 13.49 per cent. 

 Which figure is correct? 



2' Schmiedeberg, 0., Zool. Sta. Naples Mitt., vol. 3, p. 373, 1882. 



