134 



Crustacea is formed by a secretion of equal consistency from every 

 part of the body, Avhereas the Mollusca have a muscular attachment 

 to the columella, and increase the growth of their shell by an exu- 

 dation, not from the whole body, but from a particular organ ; the 

 mantle being the sole agent charged with that facult}^ It is further 

 argued by the šame distinguished naturalist that the Co\vry mušt lose 

 the power of forming the inner chambers of the columella anevv, after 

 having once passed that early process of development \vhich hiduces 

 their formatiou. " How is it possible," asks M. Deshayes, "that 

 the animal can, under the circumstances of its nature, secrete a new 

 shell from all parts of the body at once, and with all the different 

 phases of colour exhibited in the original, when it has reached to an 

 advanced condition of its existence ? " 



It is, however, certain that the Co\vry is enabled to efFect a very 

 important change in the shell during one or more periods of its 

 life ; and I think the fact may be fuUy established without prejudice 

 to the excellent arguments of my illustrious contemporary. From 

 the testimony of a gentleman who worthily employs the opportuni- 

 ties afforded him as a Navai Officer to the advancement of science, 

 ■vvhose veracity is beyond all question, and ■vvhose communication 

 (given verbatim)* contains nothing more than a simple narrative of 

 the phsenomena of \vhich he was himself an eye-witness, it may, I 

 thinlv, be deduced that it is the outer wall of the shell only \vhich is 

 reconstructed, the columella, with its spirai compartments, remain- 

 ing undisturbed. The animal does not quit the shell, as Lamarck 

 supposed, but dissolves the outer portion with its acetose juices. 

 Ali visible trace of the shell may be thus removed without weakening 

 M. Deshayes' proposition, founded on the circumstance of the mantle 

 being the only organ charged with the secretive flaid. The mantle 

 is always capable of extension over the shell, and the šame power 



* Lieut. J. B. Hankey, R.N., to Loveli Reeve. 

 My dear Sir, H.M.S. Collingwood, August 6th, 1844. 



Will you allow me to oflfer yon a few remarks oa the habits of the Cyprsea as re- 

 gards the fact of its making a new shell, at an advanced age, of which process I 

 have been myself in more than one instance an eye-witness ? i have seen the Co\vry 

 crawl iuto some hollow or sheltered place, evidently for some predetermined pur- 

 pose. The growth of the animal appears to increase too large for its cell ; it 

 gradually swells and cracks the shell, and I think that some powerfnl solvent or 

 decomposing fluid is distributed over the outer surface by the mantle of the fisb, 

 for it gets thinner in substance, and the colours duUer in appearancc. The shell 

 then entirely disappears, the Cowry becomes, to all appearance, a naked moUusk, 

 vpith no other coveriug than its membranous mantle, and in a sbort time secretes 

 a thin layer of glutinous matter which in a few days obtains the fragile consistency 

 of shell-lac. From this step its growth is more rapid, and it becomes more and 

 more cousolidated iuto the adult shell. \Vben in the first stage of renewal it has 

 the appearance of shell-lac it is always of the Cymba form, but I have never suc- 

 ceeded in preserving any specimens in this statė on account of their extreme fra- 

 gility. 



Trusting that you may raake some use of these notes, and that (as I have a good 

 dredge with me) I may, likę Mr. Cuming, succeed in bringing home something 

 ■worthy of notice, I shall conclude myself, my dear sir, 



Yours very truly, 



John B. Hankey. 



