Abstract
Middle silk gland of the silkworm in embryonic stage (120 hours after blastokinesis)has been observed electron microscopically. Comparing with the posterior silk gland in the same stage, rough ER was much less developed in the middle silk gland cells and dilatation of the ER cavity was hardly observable. Golgi apparatus is also not well developed and the sericin globules were not found. It is suggested that synthesis and secretion of protein are slight at this stage of development. In nuclei, a number of nucleoli and chromatin blocks are observable. They are usually smaller in size than those in the posterior silk gland and are not attached to the inner nuclear envelope.
These results suggest that there is some delay in the commencement of the synthesis and secretion of fibroin and sericin.
