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FIGURE 18. Parthenogenetically activated Spisula egg seen at metaphase of 1st polar body spindle stage. Egg
diameter is 60 microns. Compensator orientation is near extinction for spindle body. Retardation is about
25 À.
FIGURE 19. Same kinds of cells at same stage as to those in gure 18 but after about 5-10 minutes treatment
With 10 % DMSO in sea water. Note partial shrinkage of the cells, great increase in aster size and retardation
and general increase in spindle size. Extinctions are about 50 À. Figures 18 and 19 are taken near extinction
so that retardation cannot be compared in the two micrographs by comparing photographie density.
FIGURE 20. Spindle area of a hexylene glycol treated Spisula egg xed with glutaraldehyde in sea water. Note
large numbers of microtubules. Although no comparison picture is given, this represents a considerable
increase over the number seen in ordinary spindles. >< 40,000.