Attempts are made to study the genetic regulation of mouse lens development by comparing lens differentiation in normal embryos with that in embryos of mouse strains with mutations leading to lens abnormalities (aphakia; cataract-Fraser; lens rupture; eye-less). Morphogenesis is studied by routine histological methods, histochemistry and autoradiography. Three-dimensional reconstructions of cells and eye rudiments and quantitative measurements of volumes, surface areas, etc. are used to gain insight into the evolution of cell and organ shape. Crystallin synthesis is studied by chromatography, electrophoresis, immunodiffusion methods and immunofluorescence. Cell population kinetics and the relation of cell replication to morphogenesis and differentiation will be analyzed using H3-thymidine autoradiography and stethmokinetic agents. It is hoped that the studies will lead to better understanding of the influence of gene action in lens differentiation and of the pathogenesis of some hereditary eye defects.