Eye-stalk removal in certain species of Brachyura and Astacura has almost invariably led to the initiation of proecdysis. In other decapod crustaceans, however, there have been significant variations in the results of this operation. Thus Travis (1951) found that eye-stalk ablation had no effect on the duration of the moult cycle in Panulirus argus. And in the Natantia, even in a single species, quite different results have been reported. Drach (1944) found that eye-stalk removal in Palaemon (=Leander) serratus (Pennant) led, as in crabs, to the initiation of proecdysis and to accelerated moulting. In ignorance of this work I repeated some of the same experiments and found that eye-stalk removal in P. serratus led to slower moulting (Carlisle, 1953 a)— a result quite opposite to that of Drach. Scheer & Scheer (1954) confirm my results in the same species.