THE CYTOPLASM 



45 



of a thousand diameters and upwards, with the same object stained 

 in thin sections after fixation by picro-acetic, sublimate-acetic, and 







Fig. 19. — Section through a nephridial cell of the leech, Clepsine (drawn by Arnold Graf from 

 one of his own preparations). 



The centre of the cell is occupied by a large vacuole, filled with a watery liquid. The cyto- 

 plasm forms a very regular and distinct reticulum with scattered microsomes which become very 

 large in the peripheral zone. The larger pale bodies, lying in the ground-substance, are excretory 

 granules {i.e. metaplasm). The nucleus, at the right, is surrounded by a thick chromatic mem- 

 brane, is traversed by a very distinct linin-network, contains numerous scattered chromatin- 

 granules, and a single large nucleolus within which is a vacuole. Above are two isolated nuclei 

 showing nucleoli and chromatin-granules suspended in the linin-threads. 



other reagents. 



The comparison leaves no doubt that the normal 

 structures are in this case very perfectly preserved, though the sec- 

 tions give at first sight an appearance somewhat different from that 



