At the present time, this laboratory is engaged in studies involving the isolation, purification, and fractionation of extracellular matrix components from normal Rana pipiens embryos and various interspecific arrested hybrid frog embryos formed by fertilizing the eggs of R. pipiens with the sperm of different species, such as R. catesbeiana and R. escclenta. In addition, cells from normal and arrested hybrid embryos are being treated in vitro with extracellular matrix components to see if attachment to glass, reaggregation, or locomotion are altered by these macromolecules. Alterations in cell contact behavior are being monitored with time-lapse cinemicrography. Isolated extracellular matrix components will also be microinjected into normal and hybrid embryos in attempts to induce precocious invagination in normal embryos or correct morphogenetic defects in arrested hybrid embryos.