6o DESCRIPTION OF PLATES. 



[The figures were all drawn with Zeiss oil-immersion 2mm., oc. 12, and have been 

 reduced one-third, giving a magnification of 1,000 diameters.] 



Plate VIII. 



Trirhabda virg&ta {Family Chrysomelidce). 



Fig. 1. Equatorial plate from somatic tissues of a male pupa, 27 large chromosomes, 

 1 small one. 



2. Equatorial plate from an egg follicle, 28 large chromosomes. 



3. Equatorial plate of spermatogonium, 27 large chromosomes, 1 small one. 



4. First spermatocyte, synizesis stage. 



5. First spermatocyte, early spireme stage, showing unequal pair of chromo- 



somes. 

 6-7. First spermatocyte, later growth stages. 

 8. First spermatocyte, prophase. 

 9-12. First spermatocyte, metaphase. 



13. First spermatocyte, equatorial plate. 

 14-15. First spermatocyte, anaphase, showing separation of the elements of the 

 unequal pair (I and s). 



16. First spermatocyte, daughter plates. 



17. Second spermatocytes, equatorial plates. 



18. Second spermatocytes, equatorial plates showing V-shaped chromosomes. 



19. Second spermatocyte, early anaphase, the small chromosome in metakinesis. 



Trirhabda canadense. 



20. Equatorial plate from egg follicle, 30 large chromosomes. 



21. Equatorial plate of spermatogonium, 29 large chromosomes, 1 small one. 



22. First spermatocyte, growth stage showing the heterochromosome group. 



23. Heterochromosome group, f = plasmosome, /= large heterochromosome, 



5 = small heterochromosome. 

 24-27. First spermatocyte, metaphase. 



28. First spermatocyte, equatorial plate. 



29. First spermatocyte, equatorial plate, small member of the unequal pair only 



present. 



30. First spermatocyte, daughter plates. 



31. Second spermatocytes, equatorial plates. 

 32-33. Second spermatocytes, prophase. 



