257 



forms in marine deposits. It might be that the diatoms lived 

 now in the fresh water and now in the sea. He understood 

 that the diatoms were found attached to pieces of pumice as if 

 grown there ; that would show that they were subsequent to 

 the deposit, though the diatoms might have come a long 

 distance, and lived since the age of the deposit. 



The Secretar}^, referring to the paper, said the Coconeis 

 Mexicana was attached to the deposit. As to the mixing of 

 deposits, it was easy to see that fresh-water species might be 

 carried into marine deposits, but it was more diflScult to see 

 how marine forms should be carried up a river, as they would 

 be rapidly killed by fresh water. 



The Chairman said that his impression rather was that the 

 killing of fresh-water forms in the sea, or marine forms 

 in fresh water, was not so invariably the case as might be 

 supposed. No doubt some forms were extremel}^ sensitive. 

 There were certain star-fish which could hardly be obtained 

 perfect, except by dropping them into fresh water out of the 

 net, and so give the creature no time to destroy itself. On the 

 other hand, he thought there were a great many forms that 

 could be transferred from sea water to fresh water by adding 

 more and more fresh water as the creature got to bear 

 the change. And as minute fresh-water forms got to the 

 mouths of rivers, they got more tidal water, and so passed 

 through a process of acclimatization to a greater extent than 

 people were prepared to give credit for. He thought it quite 

 possible that many forms had, by such a slow process of 

 transference, got changed from salt water to fresh or fresh 

 water to salt, as the case might be. He moved that the thanks 

 of the meeting be presented to Dr. Edwards for his communi- 

 cation. 



The announcements for the ensuing month having been 

 made, the meeting closed with the usual conversazione. 



The following objects were exhibited : — 



Nitzschia, sp., living Mr. H. C. Gill. 



Mounted Rotifers Mr. C. Rousselet, 



Radiolaria, from Antarctic Ocean,) 



^^ Challenger'^ ... 



'J- Mr. B. W. Priest. 



