Nuclear lens tissue from fishes has been a valuable source of polymorphic proteins. 2. Generally, only the water-soluble proteins have been utilized. The present study describes (a) a solution that extracts both the water-soluble and water-insoluble proteins, and (b) an electrophoretic analysis of these proteins from 13 fish species to test for polymorphism. 3. The electrophoretic method includes among its features membranes that (a) consist of a gel form of cellulose acetate, and (b) are treated with glycine to reduce protein adsorption. 4. Electrophoretic patterns revealed distinct species differences. Polymorphism related to size of fish (a little documented subject) was not found in three of the species, but was demonstrated in varying degrees by the other ten species. 5. The methodology of this study is applicable to diverse biological disciplines, viz, population biology, taxonomy, and developmental biology.