106 PROFESSOR T. MCKENNY HUGHES, M.A., ON CAVES. 
that species do appear under such conditions, that we may say they have 
been modified to suit certain laws, and that they die away when the sur- 
roundings are unsuitable. As to the rate of modification, I will only- 
mention the change in the character of shells produced by the introduction 
of unfavourable conditions, such as fresh or salt water, and refer to the vast 
mass of evidence given by Darwin, in his work on Plants and Animals 
under Domestication. 
The Meeting was then adjourned. 
