STUDIES ON THE EFFECTS OF EYESTALK REMOVAL UPON YOUNG CRAYFISH (CAMBARUS CLARKII GIRARD)

1. Removal of both eyestalks causes a shortening of the following intermoults in Cambarus clarkii. The removal of a moult-inhibiting substance produced in the eyestalks is accepted as a reasonable explanation. 2. The methods employed have been such as to show: (a) that the processes leading up to moulting can be initiated in the absence of the eyestalks; and (b) that the effect upon moulting is associated with the absence of the eyestalks, not with the shock of their removal. 3. Injury other than eyestalk removal does not shorten the intermoult when performed early in the intermoult. 4. Eyestalk removal always results in death, but the processes related to viability which are affected by eyestalk removal can be distinguished from the moulting processes which are affected by the same operation, although there is an apparent correlation between moulting and viability.