Whether a direct endocrine factor from the eyestalk X-organ-sinus gland neurosecretory complex is involved in our observations remains to be elucidated. Most likely, however, elevated levels of 20-hydroxyecdysone, the arthropod molting hormone, are not involved. Although lobsters rapidly enter premolt immeddiately following eyestalk ablation ,after about 4 postablation molt cycles the levels of ecdysteroids and the molt cycle intervals approach those of the intact controls .By using lobsters only after several postablation most cycles (see Materials and Methods) , we have minimized the effects of trauma and shortening of the molt cycle interval.