10 THE AMERICAN MONTHLY [Jan 



that if the diatoms were cleaned with acid and were not 

 properly washed afterwards some of the mounting- media 

 would be affected in the way sug-gfested, the perfection of 

 the structure in his slide was no doubt due to the fact that 

 the material had not been previously over-cooked. 



The President thought that in considering the special 

 forms which silica might take in the structure of a diatom 

 a possible explanation mig-ht be found on the theory that 

 the process of deposit might be a vital process and not a 

 mechanical one. 



Mr. Ingpen said he was much inclined to this view, and 

 often thought that the development of a diatom mig-ht be 

 somewhat the same as the formation of a shell, where the 

 animal absorbed lime in a soluble form on one side and de- 

 posited it in an insoluble form on the other side. The ter- 

 tiary structure might possibly be the very origin of the 

 diatom. 



On Some Micro-Cements for Fluid Cells. 



BY CHARLES F. ROUSSLETT. 

 BEAD BEFORE THE QVEKETT CLUB. 



Three years ago I read a note on Clarke's Spirit-proof 

 Micro-Cements, which had proved reliable for many years 

 in securely sealing micro cells containing methylated 

 spirit. I then recommended this same cement for cells 

 containing watery fluids. It appears, however, that I too 

 hastily jumped to the conclusion that, because this 

 cement is good for spirit mounts, ii would also be equally 

 good for watery fluids, a conclusion which seems natural 

 enough. After three years' experience I must pronounce 

 it a complete failure as regards watery fluid mounts, 

 while the spirit mounts remain as good as before ; and 

 I hasten to communicate these facts, so that others may 

 profit by my experience. 



The possession of a thoroughly good and reliable 

 cement for fluid, and especially watery fluid mounts, is so 

 important to microscopists, that I hope all who have any 



