Metaphyta Spirogyra. 



79 



prehension of the phenomena of karyokinesis to bear that 

 structure in mind. The first stage consists in the partial 

 or complete disappearance of the fibrillae, or network, and 

 the assumption of a more markedly granular character by 

 the protoplasm ; the granules then unite into the form of 

 curved rods or threads and arrange themselves parallel to 

 the long axis of the nucleus. This is known as the spindle 

 stage in division (fig. 20, iv.). At the same time the proto- 

 plasm of the cell generally aggregates round either pole of 



FIG. 20, KARYOKINESIS AND CELL DIVISION. (Strasburger.) 



the spindle and exhibits a radial arrangement of its granules. 

 The next stage consists in the appearance of a plate or 

 thickening round the equator of the spindle, known as the 

 nuclear, or equatorial disc. The equatorial disc next splits 

 into two plates, either half travelling to either pole to form 

 the two new nuclei (fig 20, vi.). 



The protoplasm of the cell itself has meantime been 

 undergoing the preliminary alterations necessary to the 

 formation of a new cell- wall between the two nuclei. These 

 changes consist in the differentiation of a special plate of 

 protoplasm across the middle of the cell. In this there 

 appears a deposit of cellulose, which gradually increases in 



