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Dileptus, a common holotrich, may function as a predator upon a variety of metazoan animals representing such varied phyla as Cnidaria, Platyhelminthes, Aschelminthes, Annelida, and Mollusca. Very young animals and wounded animals are especially vulnerable. Effective predation is directly related to the concentration of Dileptus to which the victim is exposed.

Four long bipolar planarians were discovered in a stock culture of asexual Dugesia dorotocephala. Such worms have not been previously reported. Eyespots, auricles, and responses to stimuli were normal in each head-end, and functional pharynges were present. Worms in the stock culture had not been subjected to temperature variations, chemicals, or other experimentation. It is suggested that the axial gradient was effectively flattened by a normal head-inhibiting factor being unable to diffuse to the posterior end.

A number of drugs, known as goitrogens, interfere with one or the other of the mechanisms whereby the thyroid hormones are synthesized. Whether this interference is accomplished by blocking iodination of tyrosine or by inhibiting the oxiclative coupling of iodotyrosines to form iodothyronines has not been determined (Astwood. 1955). SUMMARY AND CONCLUSIONS1. A study was made of the effect of the goitrogens thiourea, phenylthiourea and thiouracil on oxygen consumption in planarians.

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