PHYSIOLOGY OF THE NUCLEOLI ^ 61 



As the stage advances, the nucleus shows more and more the 

 feature of branching; its contents, both the nucleoU and the 

 chromatin, are apparently being increased in amount with it. 

 The migration of the nucleoli is to be demonstrated as occurring 

 very frequently. 



b. Neuronia postica, Walker (Plate 2). The silk-glands of 

 caddis-worms have been discussed by Carnoy ('84), Gilson ('96) 

 and Vorhies ('05) to a certain extent. It remained, however, 

 for Marshall and Vorhies ('06) to attempt a minute comparative 

 study of the gland-cells under different physiological conditions. 

 Quoting from their conclusions, Marshall and Vorhies found 

 that: 



1. The even optical structure of the cytoplasm in the cells of most 

 normal glands become decidedly changed after activity. 



2. The activity of the gland causes the membrane on that surface 

 of the nucleus Which lies nearest the outer margin of the gland to 

 become irregular, the most noticeable feature of its irregularity being 

 the pointed processes extending into the cytoplasm. 



3. This nuclear membrane may often become indistinct. 



4. The secretory activity does not cause the nuclei to become 

 swollen. 



5. No plasmasoma or other structure is formed in the nucleus during 

 secretion. 



6. As a result of activity the 'nucleolus' becomes very irregular in 

 shape. 



As has been said in the preceding section, there has been a 

 considerable difference of opinions as to the nature of the two 

 stainable materials in the nucleus of the silk-gland cells of in- 

 sects, since Korschelt ('96, '97) insists that the larger granules are 

 the chromatin, and nucleoli are represented by smaller particles, 

 while Meves ('97), Flemming ('97), Henneguy ('04) and Mar- 

 shall and Vorhies ('06) express opinions that are exactly opposite 

 to that of Korschelt. 



Vorhies' ('08) work on the development of the nucleus has 

 finally settled the question in favor of the view that the nucleoli 

 are represented by smaller particles, and at the same time, his 

 studies enabled him to suggest that the ''nucleolar material bears 

 a direct relation to the glandular activity," since he observed the 



