1. The specificity of a number of samples of methyl green for egg-shell material in Fasciola hepatica was investigated.
2. A method for distinguishing between specific and non-specific stains by paper chromatography is described.
3. Specific stains gave almost identical chromatograms with an Rf value of 0.83 for both green and violet constituents. Non-specific samples gave chromatograms with an Rf of 0.65 for the green constituent and an Rf of 0.84 for the violet constituent. The liquid phase used was a mixture of organic solvents in the following proportions: ethanol, 100; water, 80; n-butanol, 100; cellosolve, 100.
4. The application of this technique has led to the production of a methyl green, named Methyl Green M.2, specific for shell material in Fasciola.