130 



CYTOLOGY 



CHAP. 



vesicles, then the walls of these vesicles break down to produce a common 

 nuclear cavity, in which, however, the regions of the vesicles can still be 

 recognized by the slightly denser core of chromatin occupjdng what was 

 formerly their axes. In prophase the chromosomes condense again in 

 the limits of these vesicles (Fig. 60, A-E). 



In Locusta viridissima (Otte, 1907) the chromosomes of the spermato- 



FiG. 60. 



Formation of chromosome vesicles in the spermatogonia of Orthoptera. (A-E, Phrynoteitix magnus, after 

 Wenrich, B.M.C.Z.H., 1916; F, Brcujtystolu magna, after Sutton, B.B., 1903 ; G, H, I, Locusta viridissima, 

 after Otte, Z.J. A., 1907). A, B, C, successive stages in the formation of the resting nucleus out of the telo- 

 phase chromosomes; D, E, prophase; F, early prophase; G, telophase; H, resting "nucleus " ; I, prophase. 



gonial telophases do not come into contact at all, but each one forms 

 a separate little nucleus, or karyomere, by itself (Fig. 60, G-I.) No 

 common nuclear membrane is formed to enclose them, but they remain 

 separate from one another, with cytoplasm extending in between them. 

 This account refers to the earlier spermatogonial divisions. In the last 

 one before the meiotic phase a compound nucleus is formed in the usual 

 way. 



Karyomere formation — i.e. the formation of a separate little nucleus 



