A CYTOLOGICAL STUDY OF SECRETORY PHENOMENA IN THE SILK GLAND OF HYPHANTRIA CUNEA

¹ WASHINGTON UNIVERSITY, ST. LOUIS

1. In the silk gland of Hyphantria cunea, three regions are distinguishable; a posterior, or secreting region; a middle region, or reservoir; and an anterior, or conducting region.

2. The nuclei of silk gland cells are greatly branched in the posterior region, but tend to be more flattened and less branched in the more anterior regions.

3. Three types of bodies are found to be present in each nucleus; the small basophilic granules, or chromatin; the intermediate acidophilic bodies generally termed nucleoli, but here called nuclear bodies; the relatively large, spherical body containing vacuoles and corresponding to a true nucleolus, hence called a "nucleoloid body."

4. The nucleoloid bodies appear to give rise to the nuclear bodies which pass out of the nucleus into the cytoplasm.

5. Cytoplasmic granules exhibit the same staining reactions as nuclear bodies and are approximately the same in size when they occur in the region of the nucleus.

6. Mitochondria are present in all parts of the gland, but only in the posterior region do they show definite orientation.

7. Two membranes are present along the course of the gland, and external tunica propria, and an internal tunica intima.

8. Two substances regularly appear to constitute the silk thread in the anterior region. This condition is found to continue more posteriorly after fixation with the Champy, Gatenby, Benda, and Bouin methods.

9. A substance similar to mucous surrounds the silk thread in the middle region but does not extend into the anterior portion. The origin of this substance has not been determined.