340 NATURAL HISTORY OP 



the glass cover may be removed, as it is impossible to 

 see the details of many objects through the cover. A 

 good way to accomplish this is to get a small pill-box 

 (glass capped if possible) and fix it to the slide, cutting 

 off from the bottom so much as may be above the 

 required depth, and leaving the lid removable to serve 

 for the cover. The cell so formed may, up to the lid, 

 be finished with white zinc cement, and ringed like an 

 ordinary cell. By this means a not unattractive mount 

 is obtained, which has the additional advantage of a 

 movable cover glass, so as to admit of the close exami- 

 nation of the object with high powers. Where possible, 

 both transparent and opaque mounts should be prepared. 

 All slides should be kept in a flat position in a cabinet, 

 and it is very useful to have labels of different colours 

 for the different classes, e.g. white for hydroida, pink for 

 polyzoa, and so on, with different shades to distinguish 

 British and foreign species. 



