1. Ovarian tissue from Bombyx mori L. larvae about to pupate was cultured in Trager's (1935) salt solution and 10 per cent hemolymph, with indifferent results. Improvement of cultures was sought by modifying the culture medium.
2. To reduce the activity of the tyrosinase, hemolymph for culture medium was heated for 5 minutes at 60°C., and the coagulated protein removed.
3. A physiological solution was formulated containing cations and amino acids as they occur normally in silkworm hemolymph. In both hanging-drop and small tube cultures use of this medium brought about increased cell number, improved cell appearance, more rapid mitoses, and longer life of cultures.
4. To the solution formulated from analyses, tryptophan, cystine, cysteine, malate, fumarate, succinate, and α-ketoglutarate were added after testing individually, resulting in improved growth in cultures.
5. Use of a silkworm egg extract prepared 4 to 5 days after acid treatment produced an increase in cell number.
6. In small roller tube cultures, when the new medium was changed twice a week, the cells spread over the walls of the tube in 4 or 5 days (Figs. 8 and 9), rapid mitoses were observed after 2 weeks, and transparent active cells were present at 3 weeks. Subculturing was not attempted.