86 The Microscope. 



sists of two parts, one the cell proper, being a ring on a thin 

 disk-like base, the disk giving it a broad surface for attachment 

 to the glass; the second part is the cover which slips over the 

 vertical ring like a cap, and makes the cell air and dust tight. 

 The object is placed within and covered b}' the cap, which must 

 be removed whenever the object is to be looked at. The con- 

 trivance can be used onl}' with those specimens that are mounted 

 dry, that is, with no preservative medium except the air that 

 surrounds them. There are not many specimens that can be 

 dried successfull}'^ to serve as microscopic objects. Some that 

 exist naturall}^ in the dry state can be so treated, but as a rule it 

 is better to mount in some fluid medium, especially if the object 

 is naturally moist. Minerals, some fungi, and similar things 

 can be preserved dry. 



editor;s 



^DEPARTMENT 



^^: 



This being one of the " r " months the microscopist may turn 

 his attention to^ the o^^ster. But it is chiefly as an interesting 

 subject for those leisure hours or moments of the evening, 

 when everything is quiet, when the children are in bed, and 

 there is no one to " bother round," It is then that he may 

 carr}^ into his " den " a few oj^sters, refusing to answer such 

 questions as, " Do 3'ou mean me to understand that you can find 

 bugs in them ? " or, " I think it's real mean in you to find things 

 in oysters." There may be not exactl}'^ " bugs " in oysters, but 

 there are " things." And it is these things which will give the 

 microscopist a good chance to show his skill in manipulation, 

 his skill in the use of his e3'es and of his objectives, as well as 

 the quality of his optical outfit. This list does not include his 

 stock of patience; he will need an extra suppl}^ of that. The 

 special objects to be studied are worthy of extended considera- 

 tion, not only because the}^ may be used as tests for objectives, 

 eyes and patience, but on account of their simple 3'et interesting 

 structure and habits. The}^ are certain animal parasites which 



