268 LETTERS FEOM C. DAEWIN, ESQ., 



the epidermis of Balanus Icevis (of wliiGh I send a valve, not to be 

 returned) is equally protective ; now this membrane is so weak, 

 that I cannot believe it could resist mechanical wear and tear, 

 sufficient to wear into solid shell. So again Laminaria (when 

 not uneven, and so slightly ploughed up, like cracked epidermis), 

 though not hard, is not at all excavated; again, I have specimens 

 on two pieces of slate rocks (one rather soft), which contained no 

 calcareous matter, and were not in the least affected ; whereas a 

 third specimen of hard marble was excavated. 



(5) The cement-ducts miffht pour an acid over any part of the 

 basis ; but that they do so is a mere hypothesis. In Lepas fas- 

 ciularis they must I think secrete some gas (carbonic acid gas ?). 

 I should have remarked that owing to the generally reticulated 

 state of the cement round the central hollow^ lime dissolved 

 under the central hollow might easily escape. 



This is the state of the case, as far as I can make it out. Will 

 you forgive the length of this letter, and tell me what you think? 

 And further, will you see whether you have specimens of Yerruca 

 attached to any softish rocks or substances, without calcareous 

 matter, and look and see if they act on them ? 



In two weeks' time I shall positively alJ last, after a quite 

 ridiculous lapse of time, look at your Alcippe, which I have 

 never done yet ! Have you anything new (or any. fresh speci- 

 mens to spare) on this most curious genus ? I should be pleased 

 to hear that time or inclination had led you to look at what I 

 have said on the sexes of Ibla and Scalpellum, about which I 

 remember once writing to you ; and which facts appear to me 

 curious. 



Again I beg forgiveness for the length of this letter, and re- 

 main, 



My dear Sir, 



Yours very faithfully, 



Chaeles Daewik. 

 A. Hancock, Esq. 



I do not think my wretched schoolboy MS. on the outlandish 

 MoUusca has been returned ? Has it ? 



