Developmental progression of spindle formation and spindle morphology. (A) Experimental design. Zygotes were treated with 1-butanol at 15 h AF and released by washout at 24 h AF. At hourly intervals from 24.5 to 27.5 h AF, a control dish was fixed and another dish was treated with monastrol. At 38 h AF, the monastrol-treated zygotes were fixed and labeled. (B) Percent of butanol-synchronized control zygotes that had not yet formed spindles (triangles) at the indicated times, and the percent of monastrol-treated zygotes with aberrant spindles at 38 h AF (circles). Cells that had divided were not included in this analysis. Control and treated populations were significantly different at all time points (single asterisk indicates P < 0.05 and double asterisks indicate P < 0.01). (C) Percent of telophase, short bipolar and multipolar spindles in monastrol-treated zygotes. The vast majority of the zygotes in telophase divided normally by 48 h AF. Standard error bars are shown.