Summary1. The literature on the use of paper chromatography in taxonomic work is reviewed briefly.2. The technique of paper chromatography on disks is described and the method has been applied to a number of species ofLymnaea.3. The chromatographic patterns of the species studied are described and discussed.4. The implications of the discovery of species‐specific substances in the body surface mucus of snails are discussed, both from the taxonomic and parasitological points of view.5. The possibilities of applying two‐dimensional chromatography to the free amino‐acids of snail blood are disc