Elementary Biology. 



vacuoles. There may be one or more vacuoles in each cell; 

 indeed, in very many vegetal cells there is more of vacuole 

 than protoplasm (fig. 4 c). Vacuoles are probably reservoirs 

 for substances used in the manufacture of protoplasm or for 

 products of its disintegration. After treatment with certain 

 reagents, or in some cases without such treatment, the proto- 

 plasmic matrix is found to be composed of a sponge-like 

 arrangement of threads or fibrillae (fig. 2) interlacing with 

 one another and forming a supporting framework, while the 

 interstices are filled with a more fluid homogeneous sub- 



Fi. i. DIAGRAM OF AN 



ANIMAL CELL MUCH MAG- 

 NIFIED. (Schafer.) 



FIG. 2. DIAGRAM OF AN ANI- 

 MAL CELL WITH TWO NUCLEI 

 AND SHOWING INTRACELLU- 

 LAR AND INTRANUCLEAR 



NETWORKS. (Klein.) 



, protoplasm, with vacuoles 

 and granules ; n, nucleus, 

 with intranuclear network 

 and nucleolus ('). 



stance. Most recent investigators into the minute structure 

 of protoplasm agree in thinking that the homogeneous matrix 

 above alluded to corresponds to the interfibrillar matter, 

 whilst the knots on the network, as well as the fibrillae them- 

 selves when seen end-on, furnish the granular appearance, 

 True granules are, however, also found in the interfibrillar 

 matter itself. 



In the great majority of cells, generally near the centre, 

 is to be found an oval or rounded, rarely irregular, body 

 termed the nucleus (fig. i). It is usually inclosed in a definite 

 nuclear wall or envelope. Like the cell itself the nucleus 

 consists of a fibrillar network and an interfibrillar substance. 



