130 



HEREDITY AND ENVIRONMENT 



shown in Fig. 24. But during the growth 

 period of the oocytes and spermatocytes the 

 chromosomes form a closely wound coil of 

 long chromatin threads (Fig. 31), and when 



FIG. 31. DIFFERENT STAGES IN THE DEVELOPMENT OF THE 

 EGG OF THE RABBIT. A, at the beginning of the growth 

 period showing slender chromatic threads in the nucleus; B, 

 later stage in which these threads ball up and parallel threads 

 conjugate forming the shorter, thicker thread shown in C; 

 D and E, segmentation of the long thread into chromosomes 

 each of which shows its double nature; F, later stage in 

 which the distinctness of the chromosomes is temporarily lost, 

 (After Winiwarter.) 



