Summary and Conclusions The present investigation shows that responses of snails to chemical stimuli can be measured with sufficient precision for practical purposes. Ample space, time, and numbers of snails must be employed; otherwise increased difficulties are encountered through confusing trapping action with attraction and confusing chemoperception and immediate reaction with long-term chemo-kinetic response. The progression technique described here permits precise duplication of data and allows quantitative distinctions to be made between degrees of attraction, both of which are very difficult to obtain with any short-term method known to the writer. Australorbis glabratus, Bulinus spp. and Helisoma anceps show small qualitative differences in their response to chemical agents, but quantitatively they may differ markedly in chemokinetic response, Bulinus was found fastest, Helisoma slowest, and Australorbis intermediate in rate of response to chemical attractants. Such differences in reaction rate are probably due to intrinsic differences in basal rates of locomotion, rather than to differences in chemosensitivity. Present evidence indicates that substances attractive to snails are non-specific in distribution, but that they vary either in amount or in activity, or in both, in plant-seed materials. The specific identity of such attractants is unknown, but they are water soluble, heat stable, and filterable. No group of refined chemicals has yet given evidence of strong attractive action on snails.