200 E. H. NORRIS 



of absolute cell growth, and the fourth that of lumen forma- 

 tion. These processes, although described separately, may occur 

 simultaneously. 



The first departure from the two-celled plate arrangement, 

 in the process of follicle formation, is found in a rearrangement 

 of the cells of the plate (fig. 6). The cell outlines can be made 

 out only with difficulty in most cases. But in those places where 

 they can be seen, they bound cells which are more or less columnar 

 in form. The nuclei are ovoidal or elliptical in outline and are 

 placed with their long axes perpendicular to the surface of the 

 plate. Here and there along the course of the plate (fig. 6) some 

 of the nuclei have shifted their axes and have changed their 

 relative positions. Certain of the nuclei have rotated through an 

 arc of 90 degrees so that their long axes, in their final position, are 

 at right angles to their original position in the plate. As a result 

 of this shifting process, little circlets (really spheres) of nuclei are 

 formed in the plate. 



This shifting of the nuclei is but the visible expression of the 

 changing position of the cell. For while it is impossible to ob- 

 serve the cell boundaries in most cases, it is hardly probable that 

 the nuclei shift their axes independently of the cytoplasm ; more 

 over, the few faint cell-boundaries which may be made out show 

 the same changes in position as do the nuclei. Further, it is 

 usually found that at the point from which a nucleus has shifted 

 toward the center of the plate a slight depression appears on (he 

 surface of the plate, indicating that the cytoplasm has shared 

 equally with the nucleus in this movement. From these observa- 

 tions it may be concluded that the first process manifested in 

 follicle formation is the shifting of the axes of certain cells of the 

 epithelial plate through an arc of 90 degrees. 



This process results in the transformation of the smooth 

 surfaces of the bands (fenestrated plates) into surfaces which 

 are somewhat roughened. Apparently the irregularities are not 

 due, at first, to swelhngs on the plates, but rather to the slight 

 indentations produced by the shifting of certain cells toward the 

 center of the plate as above described. In cross-sections (figs. 

 6, 13, 14) such a plate appears as a sort of beaded chain, with 



