32 



GENERAL SKETCH OF THE CELL 



coagulation-product. On the whole, therefore, it is probable that 

 careful treatment by reagents gives at least an approximately true 

 picture of the normal thread-work, though we must always allow for 

 the possible occurrence of artificial products. 



?^^^iiu 





•"■•■■■'■.•'• • "••'i 



ijpfr--;- 



%ry ■-:-■■:-. 



*• * :• <- 





• *z*\ 





Fig. 14. — Section through a nephridial cell of the leech, Clepsine (drawn bv 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 inem- 

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

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

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



One of the most beautiful forms of cyto-reticulum with which I 

 am acquainted has been described by Bofeius and Graf in the ne- 



