SECRETORY PHENOMENA IN SILK GLAND. 409 



bushes on Nonamessett Island, Mass., between August 13 and 16, 

 and brought into the laboratory at Woods Hole where the 

 animals were kept supplied with food and moisture until killed- 



METHODS. 



The caterpillars were killed by piercing the head with a pin 

 after which they were immediately fastened in a paraffined dish 

 containing Locke's solution, opened by a dorsal incision, and 

 the glands removed directly with glass needles and placed in 

 fixing fluids. Several fixing solutions were used, namely ; Bouin's, 

 Zenker's, Gilson's, for general structure, Benda's, Gatenby's 

 modified " Flemmings" for cell inclusions, Champy's method for 

 preserving and differentiating Golgi bodies and mitochondria, 

 and Regaud for mitochondria. 



Transverse and longitudinal sections, 4 micra in thickness, 

 were made of the glands and stained by various methods. The 

 results of different combinations of fixatives and stains may be 

 seen from the chart. 



OBSERVATIONS. 

 i. The Nucleus. 



(a) Historical. The nucleus of larval spinning-gland cells has 

 been found to be characteristically large and greatly branched; 

 the branches extending toward all sides of the cell. This peculi- 

 arity of shape early attracted investigators and led them to 

 study the nucleus and its contents in an effort to find some 

 possible relation between its unusual form and the active secretion 

 of silk; but it was not until Korschelt in 1896 published the 

 results of his observations upon living and fixed material that 

 a detailed account of the nuclear content of spinning-gland 

 cells appeared in the literature. From the results obtained 

 through use of a modification of the Ehrlich-Biondi stain, 

 Korschelt concluded that the larger bodies or macrosomes found 

 in the nucleus correspond to the chromatin, and the smaller 

 bodies, or microsomes to nucleoli. Meves ('97) used other 

 staining reagents and came to opposite conclusions. He identi- 

 fied the macrosomes with the nucleoli and the microsomes with 

 chromatin. More recent investigations have seemed to support 



