EXPLANATION OF PLATE 30 



All drawings maile with camera lueida from cells of the testis of the mouse 

 fixed in Carney's solution. Magnification, X 2640. 



Fig. 1. Primary spermatoc.yte in the equatorial plate stage, showing twenty 

 chromosomes, some of which are connected by chromatin like threads. Alcoholic 

 haematiu stain. 



Fig. 2. Anaphase of primary spermatocyte division, showing twenty chromo- 

 somes migrating to each pole. The chromosome marked b shows indication of 

 early splitting of chromosomes of second order. Alcoholic haematin stain. 



Fig. 3. Side view of spindle of primary spermatocyte in early anaphase. 

 Phosphotungstic-acid haematoxyliu stain. 



Fig. 4. Polar view of secondary spermatocyte in equatorial plate stage, 

 showing nineteen chromosomes. Phosphotungstic-acid haematoxylin stain. 



Fig. 3. Side view of spindle of primary spermatocyte. Alcoholic haematin 

 stain. 



Fig. 6. Secondary spermatocyte in equatorial plate stage, showing twenty 

 chromosomes: nineteen in one plane, and one marked a- at another level. Alco- 

 holic haematin stain. 



Fig. 7. Side view of spindle of secondary .spermatocyte, showing one un- 

 divided chromosome marked x beginning to migrate ahead of the others. 

 Phosphotungstic-acid haematoxylin stain. 



Fig. 8. Similar to figure 6, but showing ceutrosome divideil. The chromo- 

 some marked x is the umlivided chromosome. Phosphotungstic-acid haematoxy- 

 lin stain. 



Fig. 9. Telophase of secondary spermatocyte, showing Zwischenkorper and 

 massing of chromosomes at each pole. Phosphotungstic-acid haematoxylin stain. 



[380] 



