31 SCHMIDT ON THE C0MPAKA.T1VE PHYSIOLOGY 



extremely interesting phasnomena. I examined Ascidia {Cynthia) 

 mammillaris*. The thick fleshy sac, in which the gill and in- 

 testinal tubes, as also the liver and ovary are fixed, consist of a 

 conglomerate of large unnucleated cells, strikingly like the pa- 

 renchyma of the Cacti or many fruits. On its inner surface 

 numerous vascular ramifications are spread ; these communicate 

 with the gills. If this entire external sac is treated with water, 

 alcohol, aether, dilute acids and alkalies, in succession, the walls 

 and contents of the vessels are dissolved, and the transparent 

 colourless tissue of the above large globular cells is left, without 

 its minute structure having undergone the least change. It is 

 not altered by nitric, muriatic, or acetic acids, nor the tnost con- 

 centrated solution of potash ; in fact, an excellent method of 

 obtaining it clear and transparent is ebullition for several hours 

 with nitric acid. However, in concentrated sulphuric or fuming 

 nitric acid it slowly deliquesces into colourless fluids, the nature 

 of which I was unable to examine for want of a sufficient quan- 

 tity. The amount of water contained in this capsule is so great, 

 that 3*3175 of it left only 0*0355 = 1*07 per cent, of solid residue ; 

 so that the mantle of one entire animal of the size of half the 

 fist, and 2 lines in thickness, when dried weighed barely 0*5 grm. 

 The substance of this remarkable tissue, which was obtained 

 chemically and anatomically pure in the manner mentioned 

 first, is Ji'ee from nitrogen, as I assured myself in two experi- 

 ments upon 0*105 and 0*2065 heated with soda-lime ; when 

 heated in a glass tube it carbonizes, perfectly retaining its form, 

 and evolving the peculiar odour of carbonizing cellular tissue of 

 plants, and in the air it burns away readily and completely on 

 account of its fine state of division. When heated in glass tubes 

 to 392'^ F. it remains unaltered ; lastly, when burnt in the small 

 j)latinum vessel in a current of oxygen, as above, it yielded as 

 follows : — 



0*2168 of substance gave 0*357 carbonic acid and 0*125 water, 

 leaving 0*002 of ash (sulphate of lime in the platinum vessel). 



Hence 100 parts of the tissue, fi*ee from ash, contains — 

 Carbon . . 45*38 

 Hydrogen . 6*47 

 i. e. the composition of the cellular membrane ofplantsf. 



* With his well-known liberality Prof. Wagner gave two specimens from his 

 private collection (from Genoa and Marseilles) for this examination. 



\ This remarkable fact has since been fully confirmed by MM. Lbwig and 

 Kblliker. — Ed. 



