On the formation of the outer layer sericin in the silk gland of the silkworm, Bombyx mori L.

Abstract

The author has observed electron microscopically the formation of the outer layer sericin in the anterior piece of the middle division of the silk gland in the silkworm, Bombyx mori. The results obtained are summarized as follows:
(1) Many groups of fine granules coincided with both nucleoli and nucleolus associated chromatins are seen in the nucleus. The fine granules originated from nucleolus associated chromatin are discharged into the cytoplasm through the nuclear pores.
(2) Several kinds of cytoplasmic inclusions, such as rough surfaced elements of endoplasmic reticula, mitochondria, sericin droplets, sericin drops, granular secretions, and lipoidal bodies are observed in the cytoplasm near the nucleus.
(3) The sericin drops are formed from several sericin droplets which are produced from between rough surfaced elements of endoplasmic reticula. The sericin droplets are light in electron density, while the sericin drops are not uniform in that.
(4) From the results mentioned above, it is concluded that outer layer sericin is formed in the rough surfaced endoplasmic reticula under the intimate relation with miochondria and fine granules originated from nucleolus associated chromatin.