RE-EXAMINATION OF THE PRODUCTION OF CYCLOPIA IN FUNDULUS HETEROCLITUS WITH MAGNESIUM CHLORIDE AND ETHYL ALCOHOL

¹ Biological Laboratories, Harvard University, Cambridge 38, Mass., Marine Biological Laboratory, Woods Hole, Mass. and Department of Zoology, Oberlin College, Oberlin, Ohio

1. Under the conditions of the present MgCl₂ experiments, which followed those of Stockard as closely as possible except for temperature control, 2.0% of 11,912 surviving embryos were cyclopean; 0.3% were perfect cyclopean with an eye close to normal size, of which only three individuals hatched.

2. The optimum concentrations of MgCl₂ at the temperatures of these experiments were those which Stockard designated 18/60, 19/60, and 20/60 M.

3. With 19/60 M MgCl₂ solution, 10° C. proved lethal, while 17 to 18° C. was the optimum temperature used, with effectiveness falling as the temperature increased to 26° C. It was not possible to test temperatures of 11 to 16° C.

4. At temperatures of 21.5 to 25° C., 3% alcohol in sea water was the most effective in producing cyclopean embryos with moderately well developed body form; 4% alcohol allowed only abortive axiation and 5% alcohol was lethal.