PRELIMINARY NOTE ON HETEROCHROMOSOMES IN 



THE GUINEA PIG. 



N. M. STEVENS. 



It is the purpose of this preliminary note on the spermato- 

 genesis of the common guinea-pig merely to state some of the 

 most obvious facts concerning the unequally paired heterochro- 

 mosomes as they appear in the first spermatocytes. In the 

 later growth stages a characteristic heterochromosome (Fig. I , x) 



-.-x 



X I 



a D 



'W 

 4 5 



FIG. i. First spermatocyte growth stage. X = the heterochromosome. Mag. 

 2,000. 



FIG. 2. Prophase. 



FIG. 3. First spermatocyte metaphase, tangential section of spindle showing 

 the heterochromosome X. 



FIG. 4. Anaphase. 



FIG. 5. The heterochromosome; a, b, c, from sections of Flemming material; 

 c, d, from acetocarmine preparations. Mag. 2,000 for all of the figures. 



121 



