. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. O CONTROL X 10 Mg/L A lOOMg/L. 80MIN. AFTER FERTILIZATION "° EXPOSURE BEGUN 11 MIN. AFTER FERTILIZATION 23°C 140 FIGURE 1. The three curves on the left represent first cleavage, the others second cleavage. The different degrees of retardation and blocking of Arbacia-egg cleavage are shown in Table II, beginning with the most active mustard at the top. Concen- trations are expressed as millimols per liter. The grades of effect are the same as those used to quantitate effects of carbamates (Cornman, 1950). Where develop-
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. O CONTROL X 10 Mg/L A lOOMg/L. 80MIN. AFTER FERTILIZATION "° EXPOSURE BEGUN 11 MIN. AFTER FERTILIZATION 23°C 140 FIGURE 1. The three curves on the left represent first cleavage, the others second cleavage. The different degrees of retardation and blocking of Arbacia-egg cleavage are shown in Table II, beginning with the most active mustard at the top. Concen- trations are expressed as millimols per liter. The grades of effect are the same as those used to quantitate effects of carbamates (Cornman, 1950). Where develop- ment was not completely blocked, retardation of the first cleavage was determined from graphs like Figure 1 and then placed in one of three grades: lOO^o or more, 10% to 99%, or less than 10% increase in the time required to reach 50% first cleavage as compared with the controls. Weaker effects were detected as retarda- tion of second cleavage or of embryogenesis. At 23° ± ° C., the temperature used for all Arbacia experiments, 50 per cent first cleavage was reached usually at 52-53 minutes, but in one experiment was as early as 50 minutes and in another as late as 61 minutes. Second cleavage reached 50 per cent at 84-85 minutes, with extremes at 80 and 93 Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods Hole, Mass. : Marine Biological Laboratory
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