Whole Mounts 385 



to settle or centrifuge down at low speed. Pour off fixative and wash 

 several times with 70% alcohol, centrifuging after each wash. If a 

 mercuric chloride fixative was used, one of the washes must contain 

 some iodine. 



The easiest method for handling is the cover glass method of Chen 

 {1944 A). 



procedure: 



1. Follow the 70% washing with 80-85% alcohol: 10 minutes. 



2. Smear cover glass with albumen fixative. Place them albumen-side 

 up on slides with a bit of edge projecting beyond the slide. The 

 projecting edge can be easily grasped with forceps when it be- 

 comes necessary to move the cover glass. With a pipette pick up a 

 few drops of alcohol containing organisms. Drop them in the cen- 

 ter of the cover glass, where they will spread over its surface. The 

 alcohol will begin to e\aporate and bring the specimens in con- 

 tact with the albumen. Avoid complete drying; the edges may dry, 

 btit the center will remain slightly moist. Carefully add a couple 

 of drops of 95% alcohol onto the specimens, and then transfer the 

 cover glass to a petri dish of 95% alcohol. Slides lying in the bot- 

 tom of the dish will help to handle the cover glasses, as above. 



3. Carefully remove the cover glass from the 95% alcohol, dip it 

 gently in absolute alcohol and then flood it with 1% celloidin or 

 nitrocellulose. Drain off excess celloidin against filter paper. Wave 

 it back and forth a few seconds until it begins to turn dull and 

 place it in 70-80% alcohol. It can remain in this solution until 

 ready for staining. 



4. Any stain can be applied— hematoxylin, carmine, Feulgen — de- 

 pending upon study to be undertaken. 



5. The cover glasses are finally dehydrated, cleared, and mounted, 

 albumen-specimen-side down on a drop of mounting resin. 



comments: 



The above method is excellent and rarely fails. 



Smyth (1944) uses a quicker method and directly on slides. After 

 fixation he carries the organisms through graded alcohols into abso- 

 lute alcohol. This is dropped on a film of albumen on a slide. Place 

 the slide in absolute alcohol and continue from there to the stain. 



Agrell (1938) places suspensions of minute embryos on albumen- 

 coated slide. Allowed to almost, but not quite, dry, they become flat- 

 tened and in close contact with albumen. Dip into absolute alcohol, 



