CHROMOSOMES 



24Q 



into which the thread eventually breaks up. The 

 thread gradually grows shorter and thicker, and 

 presently becomes divided into a number of pieces 

 which are known as chromosomes. In the chromo- 

 somes the shortening and thickening process is con- 

 tinued until these bodies arrive finally at the form of 

 stumpy rods, each of which often becomes bent into 



FIG. 23. 



FIG. 24. 



FIG. 25. 



FIG. 26. 



the form of a horseshoe. Meanwhile the nuclear 

 membrane breaks down, so that the hyaline substance 

 of the nucleus becomes continuous with that of the 

 cell body surrounding it. A fresh phenomenon now 

 becomes visible. A spindle-shaped arrangement makes 

 its appearance consisting of a number of minute fibrils 

 which connect together two points the poles of the 

 spindle situated at opposite ends of the cell. The 



