1. M. Sensenbrenner, N. Springer, J. Booher andP. Mandel, Neurobiology2, 49 (1972).
2. C. Grobstein, J. exp. Zool.124, 383 (1953).
3. F. Dameron, C.r. Acad. Sci., Paris252, 3879 (1961).
4. N. Gosolow andC. Grobstein, Devel. Biol.4, 242 (1962).
5. C. Grobstein, Natl. Cancer Inst. Monograph26, 279 (1967).