88 



BASIC METHODS FOR EXPERIMENTS 



21. Place the slide in xylene or toluene, two changes, each 

 lor 5 minutes. 



22. Mount the slide in thin neutral balsam. 



23. Cover with a number o cover-slip, 24 by 50 mm The 

 cover-shp should be water-free by having been held over a flame 

 tor a tew seconds. 



24. Place slide with the section-side uppermost in a well- 

 covered slide-box. 



Protocol II. 



Staining with safranin. 



Example of object: Eggs of Chaetopterus in metaphase of 

 nrst cleavage. 



I. to 5. as in the foregoing. 



6. Replace the 80 per cent, alcohol with 5 changes of aniline 

 oil. 



7. Replace the aniline oil with xylene or toluene. 



8. Imbed eggs. 



9. Section eggs. 



10. Mount sections. 



11. Dry sections. 



^ 12. Place slides successively in xylene or toluene and descend- 

 ing grades of alcohol to 50 per cent, as in Protocol I. 



13. Remove the slide from 50 per cent alcohol to safranin 

 made up by taking equal parts of a saturated aqueous solution 

 and of a solution saturated in 95 per cent alcohol. Stain for 

 24 hours. 



14. Rinse the slide in 50 per cent alcohol. Diff-erentiate 

 under low power of microscope in dayHght in 50 per cent, 

 alcohol slightly acidulated by the addition of 2 to 3 drops of a 

 I per cent, nitric acid solution, added to 100 cc. of co per cent 

 alcohol. ^ 



15. Transfer the slide rapidly but carefully to 70, 80, 90 per 

 cent alcohol. ' > f 



16. Mount slide under microscope and flood it with clove oil 

 17- Place slide in xylene for 10 minutes with 3 changes. 



18. Mount in neutral balsam. 



