OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 137 



that the fine intracellular network can be made out with a good 

 power like Zeiss' F, or Hartnack's immersion No. 10. 



The intermediary forms between ordinary epithelial cells and 

 goblet cells that one meets amongst the epithelium of intestine 

 trachea, kc, appear to me to be just as likely indicating the 

 return of goblet cells to ordinary epithelial cells as they are 

 generally assumed to be the reverse. 



2. The Ciliated Epithelial Cells of Epididymis. 



Since 0. Becker/ it is known thatthe epithelium of the epididymis 

 is composed of ciliated columnar cells. They are always described 

 as consisting of granular protoplasm, and containing an oblong 

 nucleus and nucleolus. Examining sections through the epi- 

 didymis, hardened in spirit, of half or full grown dog, it will be 

 seen that the substance of the epithelial cells is not " granular 

 protoplasm," but is very distinctly longitudinally striated, being 

 composed of minute fibrils, arranged chiefly parallel to the long 

 axis. Under a higher power these fibrils can be traced through 

 what seems to be the thickened free border of the cell, and pro- 

 jecting as the well-known excessively long cilia. In thin sections 

 through hardened epididymis of dog, the lymphatics of which organ 

 had been previously injected by '' puncture '^ with a 2 per cent, 

 watery solution of Briicke's Berlin blue, I have no difficulty what- 

 ever to trace the connection between the fibrils of the cell-substance 

 and the cilia, even only with a moderately high power, such as 

 Zeiss' D or E, or Crouch's ^.- 



The fibrils constituting the principal part of the cell-substance 

 are, however, connected by short lateral branches into a network, 

 and the " granules " that may be seen along and between them 

 are like those in the intestinal and other epithelial cells, men- 

 tioned previously, due to optical sections of fibrils (see fig. 10 of 

 Plate VII). 



The nucleus is elliptical, and contains a distinct network with 

 the usual bright dots in the nodes. The network is either 

 uniform, like that found in the nuclei of epithelial and endo- 

 thelial cells of newt, described in the first part of this paper, or 

 there is next the membrane a special layer of circular fibrils 

 connected by radial branchlets with the more central parts. The 

 bright dots are either of uniform size, and situated in the nodes, 

 being optical sections of fibrils, or there is one or two larger 

 particles — nucleoli — found in the network. The nuclei of the 

 latter kind — i. e. with large particles — are in some places fewer 



' Moleschott's ' TJnters.,' ii, 1856. 



2 This lens is certainly a very excellent glass ; its definition is as good 

 as any Hartnack's 7 — to which it corresponds in magnifying power — 

 that I have examined. 



