xm] RESTING NUCLEUS 197 



the telophase a spiral chromatinic thread appears ; the outer 

 part of the chromosome disintegrates, and the spiral thread 

 elongates and sends out branches which join those of neigh- 

 bouring threads, so forming the nuclear reticulum. In the 

 prophase of the next division the anastomoses are with- 

 drawn, and the spirals contract to form the chromosomes. 

 She points out that this means that the chromosomes of one 



FIG. 25. Chromosomes emerging from nuclear network in Hemiptera, from 

 WILSON (1909 b}. i 5, Spermatogonial prophases of Pbrynotettix . 

 i, Reticular nucleus with irregular chromatin masses ; 2, 3, these masses 

 becoming resolved into spirals ; 2, side view, 3, polar view ; 4, 5, spiral 

 threads becoming shortened and thickened ; 6 8, emergence of elongated 

 chromosomes from reticulum of spermatocyte of Lygaeus ; the thick 

 double rods are the X- and r-chromosomes. 



division are not identical with those of the telophase .of the 

 preceding, but are formed endogenously within them. 



In the spermatogonia of various insects, especially certain 

 Hemiptera and grasshoppers, and also in other forms, a 

 somewhat analogous condition has been described. In the 

 resting nuclei the chromatin is distributed in masses, the 

 number of which is probably the same as that of the chromo- 

 somes in the preceding division. When the transition to the 



