108 Mr. P .H. Gosse on the Sub -basal Membrane o/Adamsiapalliata. 



what advanced, I easily removed it from its attachment entire, 

 revealing the form of the shell. Of this I found that there 

 existed only the middle whorl, the apical whorls having been 

 broken off, apparently a long time since, and the whole of the 

 body-whorl being deficient. The portion that remained of the 

 shell was closely invested with the membrane, of a translucent, 

 dark-greenish horn-colour; and this was projected from the 

 broken edge of the shell, and continued alone, as a new body- 

 whorl, formed wholly of membrane. This adventitious whorl 

 had followed the general course of the shell-spire, but was looser 

 and more elongate, resembling the spire of a Vermetus ; it was 

 projected for a full inch beyond the broken termination of the 

 shell, and ended iu a wide, irregularly-rounded mouth, with the 

 inner lip greatly receding. 



The substance of this membrane was firmer and tougher than 

 that of the film above described ; but under the microscope it 

 agreed with it in structure, except that it was denser. I then 

 proceeded to examine it chemically. 



A large piece cut out, and laid on a plate of thin glass, I first 

 dried, and then exposed to a red heat : it charred, without losing its 

 form. I then cut out other portions, and tested them successively 

 with the following reagents : — alcohol, water, solution of potash, 

 acetic acid, Pettenkofer's test, nitric acid, and hydrochloric acid. 

 Of these, alcohol, water (cold and boiling), solution of potash 

 (cold and boiling), acetic acid (cold and boiling), produced only 

 a negative result, the membrane remaining perfectly unaffected 

 by each. Pettenkofer's test evolved no colour. Nitric acid 

 (boiling) at once caused the membrane to dilate and thicken, 

 and in a few minutes quite dissolved it, without any colour, except 

 the yellowish tinge produced by the liberated colouring matter 

 of the substance. Hydrochloric acid (boiling) reduced the mem- 

 brane to a very thin film, but did not quite dissolve it : no colour 

 was evolved with this test. 



The boiling was performed in a watch-glass over a flame. 



Not the least effervescence was discernible from the immersion 

 of the membrane in either of the acids while cold ; nor any in 

 the heated state, except what was due to the ebullition. 



From all these tests, it is perfectly evident that the membrane 

 is wo/ of a calcareous nature, and that it is composed of chitine. 

 Neither in its source (the epidermic layer), therefore, nor in its 

 composition, does it present the slightest homology with a true 

 corallum. 



Torquay, July 21, 1858. 



