CH. I] 



FORMATION OF THE SEX-CELLS 



lar to the last, i.e. it is a skein (Fig. 4, A) with longitudinally 

 split thread. Twelve bent rods appear and become shorter than 

 the bent rods of the heterotypic type. These rods then arrange 

 themselves about the middle of the achromatic spindle (Fig. 

 4, B). The twelve bent rods divide each into two by separa- 

 tion along a longitudinal line, and twenty-four rods are present. 

 Immediately twelve of these migrate toward one pole, and 

 twelve toward the other, and the cell-division follows (Fig. 4, 

 C, D, E, F). The cells then come to rest. 



E F 



FIG. 4. Homoeotypic type of nuclear division in Salamandra. (After Flemming.) 



The end result in the two types of cleavage is the same, but 

 the details are, as described, different. It is important to note 

 that the number of chromosomes is half that of the number of 

 chromosomes in the other cells of the bod}'. 



Vom Rath maintains that a fourth generation of cells appears 

 in the development of the spermatozoa of the salamander. Flem- 

 ming supposed that at the end of the third generation of cells, 

 described above, the differentiation into spermatozoa began, but 



