236 GENERAL ZOOLOGY 



appear later on the spindle are numerous small spherical bodies 

 formed from the middle portions of the chromosomes. These 

 divide as chromosomes and appear in succeeding cells descended 

 from the three. Thus as a result of the process of chromatin 

 diminution, the ends of the chromosomes are eliminated and the 

 remainder of each chromosome breaks up into numerous smaller 

 fragments. In the fourth cell, called the stem cell, the chromo- 

 somes appear in their usual form and are divided in the usual 

 manner. In the fourth and fifth cleavage, chromatin diminution 

 again takes place in one of the descendants of the stem cell. 

 As a result, there are established two kinds of cells with regard to 

 chromatin content, diminished and undiminished. In Ascaris 

 the somatic cells are derived from embryonic cells in which 

 chromatin diminution has occurred, and the germ cells from 

 undiminished cells (Fig. 144). 



