238 THE USE OF THE MICROSCOPE 



with chrom-acetic-formalin, and stain with iodine gentian- 

 violet, or iron-hsematoxyhn in 70 per cent alcohol. Mount 

 in immersion oil. 



64. Chromosomes of Tumors. — Treated as in 63. Chro- 

 mosomes counted in late prophase (Belling, 1927). 



65. Chromosomes of Drosophila. — Use XX Y females. 

 Ovary dissected out. Fixed in strong Flemming's solu- 

 tion, or in chrom-acetic-formalin. Washed in alcohol (not 

 water). Cut in paraffin. Stained with nuclear stain which 

 does not require long maceration in water. Iron hsematox- 

 ylin, with all reagents in 70 per cent alcohol, can be used. 

 Dividing oogonial cells show the required figures. 



66. Chromosomes of Drosophila. 2n + IV Animal. — As 

 in 65 (Bridges). 



67. Chromosomes of Drosophila. 2n — IV Animal. — As 

 in 65 (Bridges). 



68. Chromosomes of Drosophila. Female with Attached 

 X's.— As in 65 (L. V. Morgan). 



69. Chromosomes of Drosophila. Triploid Female.— 

 As in 65 (Bridges). 



70. Chromosomes of Amphibian. — As in 63 (Janssens). 



71. Chromosomes of Ova of Ascaris. — Fix smears in 

 Carnoy's mixture. Try iron-acetocarmine as subsequent 

 stain. 



72. Maturation Divisions in the Ova of Dendrocoelum. — 

 Try as in 63 or 71. Count the chromomeres in good 

 preparations of the pachytene. (Gelei.) 



73. Maturation Divisions in Sperm Formation in Tomop- 

 teris. — Try as in 61. Try alcoholic iron-hsematoxylin 

 or iron-brazilin on smears fixed in chrom-acetic-formalin. 

 (Schreiner.) 



74. Salivary Cells of Larvae of Chironomus, or Other 

 Flies. — Try preparation as in 63 or 73. Count the chromo- 

 meres. (Alverdes.) 



75. Cleavage in Ova of Fresh -water Snail (Planorbis). 

 Living. — Water-immersion objective, 70 apochromatic. 

 Ova of Echinus are also favorable. 



