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Heredity and Environment 





FIG. 8. SUCCESSIVE STAGES OF MITOSIS IN THE CLEAVAGE OF THE EGG OF A FISH 

 (Fundulus) showing that new chromosomes are formed inside of old ones (chromosomal 

 vesicles), that chromosomes or chromosomal vesicles persist from one division to the 

 next and that even the "resting" nucleus is composed of chromosomal vesicles. A, nu- 

 cleus at beginning of mitosis, having shrunk from dotted outline and showing chromo- 

 somal vesicles containing chromatin granules; B, each chromosomal vesicle contains 

 granules or chromosomeres which are condensing to form a chromosome; C, amphiaster 

 showing faint outlines of the chromosomal vesicles with their cntained chromosomes-; 

 D, amphiaster showing each chromosome beginning to split and the chromosomes divid- 

 ing; E, late phase of division showing daughter chromosomes at the poles of the 

 spindle and each chromosome becoming vesicular; F, still later phase, each chromosome 

 a vesicle containing chromatin granules; G, daughter nucleus showing chromosomal 

 vesicles containing scattered chromatin granules. (After Richards.) 



