62 Nature of the Genetic Material 



Fig. 6. Cycle of heterochromatin 

 in Ascaris megalocepJiala (Parascaris 

 equorum). A, Oogonium; B, hetero- 

 pyknosis in oocytes; C and D, pachy- 

 tene configuration; E-G, early pro- 

 phase of meiosis; H-J, formation of 

 tetrad; K, embryonic cells with and 

 without diminution. All cells from the 

 race univalens 2n = 2. (Feulgen stain, 

 redrawn from Lin, 1954.) 



