Coverslips 



DRY WHOLEMOUNTS 



11 



coating the sheet before cutting with the 

 thick solution which is allowed to dry and 

 then pressed under heat onto the lower 

 surface of the slide. Sheets of photog- 

 rapher's dry mounting tissue can be used 

 for the same purpose, if a photographer's 

 dry mounting press is available. This com- 

 pletes a wooden microscope slide with a 

 built-in, white-bottomed, cell. If a black 

 bottom is required a disk of black paper is 

 punched, coated with ordinary starch 



frame, the flanges of which are sufficiently 

 deep to allow a thin slide to be slipped in 

 as a cover. 



Selection of a Coverslip 



The chief difficulty in selecting a cover- 

 slip for a dry wholemount using a deep 

 cell is to find one which is thick enough. 

 The only value attaching to very thin 

 coverslips is that they permit the use of 

 high power objectives. Most dry whole- 



Fig. 7. Turning a ring on a slide. 



paste on the underside, and pressed into 

 position at the bottom of the hole. 



Numerous variations on slides of this 

 type are possible. To mount a number of 

 small objects on the same slide it is only 

 necessary to drill a number of small holes 

 at the end of the wooden slab and thus 

 secure a slide with as many built-in cells as 

 is required. Special shdes for Foraminifera 

 are made where large collections are to be 

 mounted. These consist of 3" X 1" slips 

 of black card on the central two-thirds of 

 which are printed 60 numbered divisions. 

 At each end a section of thick card is glued 

 on, so as to leave the black portion in the 

 form of a shallow rectangular cell. The 

 card so prepared slides into an aluminum 



mounts are used with low power objec- 

 tives. The thickness commercially sold as 

 No. 3 is the thinnest which should be con- 

 sidered, unless high powers are certain to 

 be used. 



Selection of a Cell 



A cell on a dry mount serves mainly to 

 support the covershp, and the thickness 

 required is therefore the primary con- 

 sideration governing selection. Where the 

 object is only a few hundredths of an inch 

 in thickness, as in the case of diatoms or 

 the smaller Radiolaria, a cement cell is the 

 simplest. For a dry mount it is difficult to 

 find a better cement than "gold size" and 

 the preparation of a cell with this medium 



