PLATE 4 



EXPLANATION OF FIGURES 



23 to 58 Acridium granulatiis Scudd. 



23 Secondary spermatogonium from young cyst. Only chromosomes and 

 cell boundary shown. Ordinary chromosomes numbered according to size 

 from 1 to 6. Sex chromosome, 2 x, ranks second in the series between ordinary 

 chromosomes nos. 1 and 2. The number 2, preceding x, indicates this rank. It 

 stains lightly. The deficiency of one no. 4 chromosome (4—) is shown by the 

 minus sign ( — ) following the no. Sex chromosome lightly stained. 



24, 25, 27, 28 Spermatogonia from various animals. Sex chromosomes (2x) 

 faintly stained and 'wooly.' Deficient no. 4 in figure 27. 



26a, b, c, d 'Wooly' sex chromosomes from different spermatogonial meta- 

 phases. 



29 to 34 First spermatocyte divisions. Members of pairs in each case are 

 separating from each other. The sex chromosome {2x) goes to one pole ahead 

 of the others. 



286 



