12C I III. NA0T1LUS. 



beforehand whether this will be an infallible remedy, 'rime only 

 can prove its efficacy. 



On page 235 of the same volume. Mr. Byne gives the following 

 supplementary notes to his former observations : 



''At the time of writing my former paper I did not possess any 

 knowledge of bacteriology, but I had come to the conclusion some 

 months before that the corrosion was due originally to the action of 

 bacteria. I am now enabled, through the kindness of Dr. Ewart, to 

 adduce a considerable amount of evidence in support of this. I still 

 adhere to the five items of "my previous summary. 



The white powdery substance upon the surface of the shells was 

 found to consist of calcium butyrate, in some instances mixed with 

 calcium acetate. It was formed by the action of butyric and acetic 

 acids upon the calcium carbonate of the shell structure. 



Since butyric acid does not occur in the atmosphere, it can hardly 

 have had an external origin. It must, therefore, have been derived 

 from fermentative processes occurring in the organic material of the 

 shell, or of adhering portions of the molluscan inhabitant. Both 

 aerobic and anaerobic bacteria are known which can cause various 

 carbohydrates to ferment, producing butyric and acetic acids. It is 

 very often the case that a portion of the liver is left attached to the 

 shell, especially to the apex. This might easily undergo butyric 

 fermentation, and, moreover, the same might occur with the adhesive 

 substance used to fix the specimen to its card. Both aerobic- and 

 anaerobic butyric bacteria exist, but the common forms are anaero- 

 bic. Hence we should expect to find the danger of spoiling in- 

 creased with imperfect aeration in closed or hermetically sealed 

 cases, in which at the same time there would be no possibility of the 

 acid products escaping. A little moisture is required to start the 

 fermentation ; hence, dry cases should escape, and even in damp air 

 the process can only lake place with great slowness, for so soon as 

 the products accumulate to a certain extent, fermentation ceases 

 until they have been removed. 



That the mischief is of bacterial Origin is supported by the follow- 

 ing fad- : 



1. Butyric acid has //ecu found. 



This could only be produced by the butyric fermentation of carbo- 

 hydrates, or even proteid substances. Acetic acid i- amongst the 

 fermentative products of butyric bacteria, and calcium acetate has 

 been found in some of the shells. 



