Royal Microscopical Sociehj. 245 



entirely upon adhesive contact caiisod by moisture or an oily 

 exudation from the scale ? If so, the effect would be enhanced by 

 previously pouring over the slide a thin solution of Canada balsam 

 in ether, so as to leave a mere trace, or suflScieut only to ensure 

 contact without the risk of spoiling the object by percolating its 

 structure. 



In English-mounted slides of diatoms and insect scales, some 

 are always found detached from the cover and on the slide, and are 

 shown well ; but such is not the case with Moller's and others ; 

 they raise their covers off the slides by a ring of cement, and in 

 many of them I have searched in vain for a solitary specimen 

 that has become detached. 



