110 



The purpose of this interesting structure is evidently to allow free 

 passage to gases through the shell and the membrana putaminis, 

 whilst liquids are effectually retained by it. 



I make this brief communication, because I am desirous of putting 

 upon record, without delay, an interesting fact which I believe to be 

 hitherto unknown ; and of suggesting to some other microscopists to 

 carry out the enquiry, — my own attention being at present differently 

 occupied. 



Biistol, September 19, 1842. 



