i8 



VETERINARY PHYSIOLOGY 



one another, but remain united by delicate lines to form a 

 spindle-shaped structure (fig. 3, i). The spindle passes into 

 the centre of the nucleus, and seems to direct the changes in the 

 reticulum. The nuclear membrane disappears, and the nucleus 

 is thus not so sharply marked off from the cell protoplasm. 

 The nucleoli and nodal points also disappear, and with them all 

 the finer fibrils of the network, leaving only the stouter fibres, 

 which are now arranged either in a skein or as loops with their 

 closed extremity to one pole of the nucleus and their open 



(3) 



FIG. 3. Nucleus in Mitosis : (1 ) Convoluted stage ; (2) Monaster stage ; 

 (3) Dyaster stage ; (4) Complete division. 



extremity to the other. The nucleus no longer seems to 

 contain a network, but appears to be filled with a convoluted 

 mass of coarse fibres, and hence this stage of nuclear division is 

 called the convoluted stage. 



The spindle continues to grow until it occupies the whole 

 length of the nucleus. The two centrosomes are now very 

 distinct, and from them a series of radiating lines extends out 

 into the protoplasm of the cell. 



The nuclear loops of fibres break up into short, thick pieces ; 

 and these become arranged around the equator of the spindle 



