OF THE INVERTEBRATE ANIMALS. 3? 



Carbon . 46-08 

 Hydrogen 6-67. 

 However, the slight excess of carbon and hydrogen may be 

 ascribed to impurity arising from a portion of the fat, colouring 

 matter, &c. being mixed with it. At all events this residue is 

 identical with the membrane of the vegetable cell ! The contents 

 of the siliceous carapace, which were soluble in potash, behaved 

 like proteine, judging from the reactions with potash, ammonia, 

 acetic acid and nitric acid (formation of xantho-proteic acid) ; but 

 their elementary constitution could not be determined with the 

 necessary accuracy, inasmuch as the residue free from nitrogen 

 is only relatively, not absolutely insoluble in potash ; a property 

 which belongs also to Payen's pure cellulose ; hence on neutral- 

 izing the alkaline solution with acetic acid, a quantity of the 

 latter is precipitated with silica and proteine. This mixture 

 yielded from 8 to 1 2 per cent, of nitrogen, and 



Carbon 48 497 



Hydrogen . . . . 6'7 6'9 



results which agree perfectly with my supposition. Hence, by 

 determining the amount of ash and nitrogen, the relation of the 

 siliceous carapace to the fat, proteine and cellulose may be ascer- 

 tained with sufficient accuracy and elegance. The pure mucous 

 masses (e. e. of course freed from the contents of the brine-ley by 

 washing with pure water), dried at 248° before treatment with 

 aether, gave as follows, — 



0*4235 substance yielded 0*191 ash, containing 0*1795 silica. 

 0*0115 phosphate of lime with a little peroxide of iron = 45*1 

 per cent. 



0*4375 of the substance gave 0*1665 of ammonio-chloride of 

 platinum = 4*35 per cent, of nitrogen (after deducting the ash). 

 The same mass, when dried at 248°, after treatment with 

 aether, hence after the removal of the fat, yielded, — 



0*2045 substance, 0*1095 ash = 53*545 per cent. 

 Proteine, fibrine, albumen and caseine contain on an average 

 15*8 per cent, of nitrogen. Taking this as a base, we have in 

 100 parts of the Frustuliee, — 



SiUceous carapace 45*10 



Fat (ovary, testicle ?) 15*77 



Proteine-substance (foot?) 15*12 



Vegetable cellular matter (mucous envelope) . 24*01 

 I therefore believe that the position advanced at the end of the 



