426 ELIZABETH KIXXEY. 



3. The Nature of the Secretion. 



The column of silk secretion is apparently composed of two 

 slightly different substances as evidenced by diverse staining 

 reactions, but further study is necessary before the exact origin 

 and nature of each is determined. 



Since in the posterior region, the silk thread appears to be a 

 homogeneous cylinder when preserved in several different fixa- 

 tives, it would seem that there is but one kind of substance 

 secreted and that this substance undergoes partial modification, 

 possibly oxidation, during its progress down the tube. 



A substance similar to mucous appears in the lumen as an 

 envelop surrounding the silk column, but no account of its 

 origin can be given. In life, it is evidently a fluid substance 

 because it is found to be present wherever a break in the con- 

 tinuity of the fiber occurs. The distinction between this sub- 

 stance that is finely granular in appearance after certain fixations 

 and the clear hyalin substance present in the same relative 

 position, following fixation in Regaud's solution, cannot be 

 determined. The latter substance has been considered as com- 

 posing the intima but the former cannot be so accounted for. 



SUMMARY. 



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 inter- 

 mediate acidophilic bodies generally termed nucleoli, but here 

 called nuclear bodies; the relatively large, spherical body con- 

 taining vacuoles and corresponding to a true nucleolus, hence 

 called a "nudeoloid body." 



4. The nudeoloid 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. 



