We are studying the process of "cortical flow" in Xenopus oocytes. Cortical flow is normally triggered at fertilization in this species, but can be triggered artificially by treatment with agonists of protein Idnase C. We have found that cortical flow (manifest as movement of cortical pigment granules) is greatly speeded by microtubule depolymerization. In preliminary work (performed using a confocal microscope at the Marine Biological Laboratory at Woods Hole, MA) we found that cortical flow is accompanied by a striking accumulation of filamentous actin at the top of the oocyte. Because of a severe autofluorescence problem with these cells, a confocal microscope is required to visualize such filaments so we intend to pursue these studi6s using the confocal microscope at the IMR. We hope to confirm our previous results, and to determine if microtubule depolymerization speeds actin filament accumulation.