254 JOURNAL OF CONCHOLOGY, VOL. 9, NO. 8, OCTOBER, 1899. 



calcium acetate has been found in some of the shells. 

 2. — The shells in the top cases that are exposed to light are 

 practically unaffected. 



This points strongly to bacteria. The deadly action of 

 direct sunlight on bacteria is well known, and may produce 

 death in from five minutes to an hour when they are in the 

 vegetative condition. Even strong diffuse daylight suffices to 

 retard or even inhibit the development of many bacteria. 

 3. — The shells in the drawers kept iti the dark are the worst 

 attacked. 



This necessarily follows from the above statement. Dark- 

 ness is favourable to the development of these fermentative 

 organisms. Within the shell the bacteria would even in the 

 top cases be protected from the inimical effect of light. 

 I stated in my former paper that the corrosion had not occurred 

 in private collections. Since its publication I have been informed 

 that some shells in a large private collection at Birmingham have 

 been badly corroded, and have caused anxiety for some time past. 

 Also, I have examined several specimens of the genus Cypnea from 

 the Gratrix Collection in Manchester. These all possessed a marked 

 vinegar-like odour. Upon being submitted to the same chemical 

 tests as the shells from the British Museum, they were found to con- 

 tain both calcium butyrate and acetate, and thus show that they had 

 been exposed to the same conditions as those at South Kensington. 



Prevention. 

 It must surely be conceded that an infallible remedy cannot be 

 given. My critics have either overlooked or paid no attention to 

 the fact that the corrosion does not appear until after the lapse of 

 about ten years. 



The suggestions received are : — 

 1. — Boiling in oil. 



2. — Rubbing over the surface with such substances as oil of tur- 

 pentine, oil of cloves, and formalin. 

 I am of opinion that these may be dismissed as ineffectual. Now 

 that we know that the corrosion is caused by bacteria, I am more 

 than ever convinced that soaking in corrosive sublimate solution, 

 combined with previous thorough cleaning, will prove effectual. It 

 must be remembered that corrosive sublimate is an extremely poison- 

 ous substance. The drawers should be thoroughly aerated at intervals, 

 to remove accumulated acid vapours, which will never be present in 

 more than minute traces. The drawers should also be kept well 

 dried. 



8, Sea View Terrace, 

 Seaton, Devon. 



