SECRETION IN FOLLICLE CELLS. 213 



Healthy follicle cells have a very characteristic refraction and 

 lie regularly arranged in the epithelial layer, as hexagonal prisms 

 with slightly rounded corners. Dying or dead follicle cells 

 exhibit a marked decrease in refractive properties, a more opaque 

 appearance, and a loss of their regular arrangement, due usually 

 to plasmolysis. In general, the cells remain in healthy condition 

 from 48 to 72 hours after implantation. 



The vital stains used were methyl green, neutral red, toluidine 

 blue, brilliant cresyl blue, nile blue sulphate, and janus green, 

 dissolved in the culture medium in concentrations varying from 

 i in 20,000 to I in 5,000. The stains were toxic in greater or 

 less degree; janus green, toluidine blue and nile blue sulphate 

 were especially so. 



The fixatives used were as follows: Bouin's; Flemming's 

 (strong formula, with acetic) ; Da Fano's cobalt nitrate modi- 

 fication of Cajal's method for Golgi apparatus (C. Da Fano, '20) ; 

 Regaud's fixative for mitochondria; formol; Kopsch's osmic 

 acid impregnation for Golgi apparatus; and Champy's fluid 

 modified for showing Golgi apparatus. For stains and combi- 

 nations of stains with fixatives, see Charts I., II., and III. The 

 fixatives served as controls for one another. The egg string 

 distal to the A egg was sectioned longitudinally. The A egg 

 could not successfully be sectioned longitudinally (for use in 

 cytological study) due to the brittleness of the fixed yolk. 

 Transverse sections were made of the A and B eggs. Sections 

 varied in thickness from 2 micra (in material fixed by Regaud's 

 method) to 5 micra (after fixation in Bouin's solution). 



IV. OBSERVATIONS. 



A. CELL DIVISION. 



Follicles were observed in culture medium for nuclear division. 

 Specimens of the "amitotic" follicle fixed in Bouin's solution 

 show what appears superficially to be a mechanism which might 

 function in nuclear division, i.e., a series of strands radiating 

 from the plasmosome, with particles of chromatin often resting 

 upon them (Fig. 2). It was expected that a study of tissue 

 cultures might throw light upon these structures. To this end, 

 follicle cells whose nuclei were in an elongated or constricted 



