The fractionation of aHydra-derived inhibitor into head and foot inhibitors may be an artefact.

A fraction has been purified from crude extracts ofHydra, termed inhibitor I, which inhibits budding as well as head and foot regeneration. This fraction has been proposed by others to contain (at least) two substances, a head inhibitor (HI) and a foot inhibitor (FI), which preferentially inhibit head and foot regeneration respectively. The present study indicates that the reported fractionation is an artefact produced by the chromatographic procedure used. Substances can be eluted from virgin Dowex 50 which preferentially inhibit head regeneration. These substances are formed in the resin if left standing in its hydrogen form. Further, we have not been able to confirm that the extract from heads preferentially inhibits head regeneration and the extract from feet preferentially inhibits foot regeneration. Rather it appears that the inhibitor I is contained both in the head and in the foot.