1. Barigozzi, C., Rend. Ist. Lombardo Sci. e Lett., Cl. Sci., 79 (1945–1946).
2. Mather, K., Proc. Boy. Soc., B, 132, 308 (1944).
3. Casperason, T., Naturwiss., 29, 33 (1941).
4. These results were partially communicated to the Congress for Experimental cytology, Stockholm, July 1947.