1892.] MICROSCOnCAL JOURNAL. 259 



which gives good results and is simpler. Buy the Crystals of 

 chromic acid and dissolve in v\\ater as you need them. Tlien take 

 the material which has been partially cleaned by the process I 

 mentioned and put it in an evaporating dish, pouring oH'as much 

 of the water as possible. Heat the bottle of chromic acid by let- 

 ing it stand a minute or two in hot water. Heat the material also 

 in the evaporating dish over the spirit lamp. Then add the 

 chromic acid and let it stand a few minutes, keeping up the heat 

 by the spirit lamp. Then pour the material into quite a quantity 

 of water in a high glass and let it settle. Wash until all the yellow 

 color disappears. Then let the material settle in a test-tube, pour 

 off as much of the water as possible and cover with strong am- 

 monia. Then wash several times again. If the forms are not 

 then clean enough repeat the process and keep on repeating till 

 they come out as you wish. 



Then, as to mounting, if you want to get a fine effect by dark- 

 ground illumination, incinerate the forms on platinum foil or thin 

 mica over the spirit lamp or Bunsen burner. This will change 

 the forms from a glossy to a milky white. Mount in balsam 

 and look at them by transparent light. They will appear black 

 or broxvn^ and seem an utter failure. Ask yourself if it seems pos- 

 sible that they should show up well by dark-ground illumination, 

 and then try it, and you will probably be as much surprised at the 

 result as I was, when by mere chance I made the experiment. 

 The forms with the binocular stand out with wonderful distinct- 

 ness, and the effect is almost equal to that of an opaque mount. 

 You have only to use dark-ground illumination on a slide of forms 

 that have not been burnt to be convinced of the superiority of this 

 method. 



And now, in conclusion, let me say that I am certain there is a 

 vast amount of pleasure in store here for any young microscopist. 

 With many a beginner the question is, what special line to take 

 up. And even many a microscopist of long standing and larger 

 experience is at times at a loss as to what he shall make a sub- 

 ject of close investigation. If any of you are in that state, or ever 

 find yourself in it, casting about for some special line of study, I 

 would advise you by all means to settle on the Radiolaria^ and 

 work at them thoroughly. First, because they are so easy to pre- 

 pare, and, secondly, because I know they will amply repay all 

 the labor you may put upon them. 



For the illustrations which accompany this article I am again 

 indebted to Mr. Robert W. Smiley, and desire here to express 

 my thanks to him for his kind assistance. 



List of Figures in the Frontispiece. 



Fig. 13. Ceratospyris Echinus. Fig. 21. Anthocyrtiiim (Anthocyrtis) Fictis. 



14. Thyrsocyrtis Rhizodon. 22 Lithopera Lagena. 



15. Periphaena decora. 23. I ithochytri.s Tripodium. 



16. Lophophaena Capito. 24. Petalospyris Flabellum. 



17. Dictyophimus Craticula. 2i. Botryocyrtis (Lithobotris) cribosa ? 

 t8. Lychnocanium Tripodium. 26. Stephanolithis (Lithocircus) annu- 



19. Lithomelissa macroptera. ■ laris. 



20. Calocyclas Turris. ' 



[the end.] 



