PIGMENT CELLS, CAPILLARIES, ETC. 143 



points with that which has already been described above for 

 the cells of the epidermis for Lumbricus. I think, there- 

 fore, that a more detailed description may be omitted, and 

 content myself with a reference to Photograph X., which, 

 however, both as regards the goodness of the section and 

 the success of the photograph, still admits of being con- 

 siderably surpassed. 



10. Pigment Cells of the Parenchyma of Aulastomum gulo 



I draw attention to these brown pigment cells observed 

 by me casually, chiefly from the fact that they show the 

 meshwork structure especially clearly and distinctly, and 

 moreover, permit the relations of the pigment granules to 

 the framework to be made out particularly well. The cells 

 investigated were obtained casually when making prepara- 

 tions of isolated muscle cells. The maceration of small pieces 

 of the body wall of Aulastomum was performed in 10 per 

 cent iodine alcohol, and lasted two days. Plate VII. Fig. 6 

 gives a picture, as true to nature as possible, of a small 

 portion of the protoplasmic framework of an isolated cell. 

 The very small pigment granules are always lodged in the 

 nodal points of the framework, yet on. account of their 

 staining properties it can be seen very plainly that by 

 no means all the nodal points contain such deposits. With 

 regard to other points, I think the figure requires no further 

 explanation. 



11. Capillaries from the Spinal Marrow of the Calf 



In maceration preparations of the spinal cord of the 

 calf, one frequently obtains isolations of rich networks of 

 the finest capillaries. If one investigates more closely the 

 finer structure of one of these capillaries (Plate IX. Fig. 1), 

 it can be seen to possess a very thin protoplasmic wall, in 

 which here and there large nuclei (n) are lodged. These 

 nuclei cause, wherever they occur, a projection of the wall 

 into the lumen of the capillary. 



In an optical longitudinal section of the wall it may 



