The movie shows the effect of pressure on the spindle of the Chaetopteris egg. 100 Atm. of pressure induces depolymerization of spindle microtubules leading to the loss of birefringence in this polarizing microscopy study. As the spindle loses its birefringence and slowly shrinks, the chromosomes are pulled to the cell surface. When the pressure is returned to 1 Atm., the spindle microtubules reassemble and push the chromosomes away from the cell surface. The movie shows several rounds of pressure increases and decreases in which the birefingence of the spindle is clearly seen with polarizing optics. The last sequence shows the same cycle using phase contrast where the spindle is not so clearly seen.