Abstract
1. Silkworm embryos decapitated before the differentiation of neuroblasts, or before differentiation of the prothoracic glands, were cultured in vitro. 2. Brainless embryos which developed from these decapitated explants detached the cuticle, suggesting that the ‘moult’ of cultured embryos does not require any hormonal action of the brain in the silkworm at least for its initiation. 3. The prothoracic gland was not found to be necessary even for occurrence of the embryonic moult. 4. The author's results obtained by embryo culture in the silkworm are contrary to those obtained by ligaturing experiments in the locusts. This difference between the two cases present important questions about the nature of the moult in cultured silkworm embryos, which must be answered by further investigations.