20 



GENERAL SKETCH OF THE CELL 



It is often difficult to distinguish between such metaplasmic bodies 

 and the granules commonly supposed to be elements of the active 

 protoplasm ; indeed, as will appear beyond (p. 29), there is reason 

 to believe that " protoplasmic " and " metaplasmic " granules cannot 

 be separated by any definite limit, but are connected by various 

 gradations. Among the lifeless products of the protoplasm must be 

 reckoned also the cell-wall or membrane by which the cell-body may 



Fig. 7 Spermatogonia of the salamander. [MEVES.] 



Above, two cells showing large nuclei, with linin-threads and scattered chromatin-granules; in 

 each cell an attraction-sphere with two centrosomes. Below, three contiguous spermatogonia, 

 showing chromatin-reticulum, centrosomes and spheres, and sphere-bridges. 



be surrounded ; but it must be remembered that the cell-wall in some 

 cases arises by a direct transformation of the protoplasmic substance, 

 and that it often retains the power of growth by intussusception like 

 living matter. 



It is unfortunate that some confusion has arisen in the use of the 

 word protoplasm. When Ley dig, Schultze, Briicke, De Bary, and 

 other earlier writers spoke of " protoplasm," they had in mind only 

 the substance of the cell-body, not that of the nucleus. Strasburger, 



