A new assay for the juvenile hormone of insects is described which permits detection of very small amounts of hormone activity.2. Using this procedure extracts of a variety of invertebrates were assayed for juvenile hormone activity.3. Juvenile hormone activity was detected in Hydrozoa, Polychaeta, Oligochaeta, Lepidoptera, Coleoptera, Decapoda, Holothuroidea, and Balanoglossida.4. The richest source of juvenile hormone outside of insects was the eyestalk of Crustacea and it is suggested that the juvenile hormone plays a role in crustacean physiology.5. The significance of these findings is discussed in relation to the evolution of humoral mechanisms.
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Schneiderman et al. (1958) studied this question.