22 DESCRIPTION OF PLATES. 



DESCRIPTION OF PLATES. 



[The figures were all drawn with camera lucida, Zeiss oil-immersion 2 mm., oc. 12 

 and have been reduced one-third, giving a magnification of 1000 diameters.] 



PLATE I. 

 Brozvn rose aphid. 



FIGS. 1-3. First spermatocyte, metaphase, aceto-carmine preparation of November 13. 



4. Second spermatocyte, metaphase. 



5. Parthenogenetic egg, metaphase of segmentation spindle. 



6. Parthenogenetic egg, metaphase of maturation spindle. The double series 



of chromosomes is numbered, here and in other figures, in order of size. 



Green rose aphid. 



7-9. First spermatocyte, metaphase, aceto-carmine preparation of November 14. 



10. First spermatocyte, prophase, showing paired chromosomes. 



11. First spermatocyte, metaphase, from section. 



12. First spermatocyte, late anaphase. 

 13-14. Second spermatocyte, metaphase. 



15. Two-cell stage of parthenogenetic egg, metaphase, showing the double 

 series of 14 somatic chromosomes. 



16 a and b. Parthenogenetic egg, prophase of maturation mitosis showing 14 



chromosomes. 



Migratory rose aphid. 



17 a and b. Winter egg, first maturation mitosis, metaphase, 9 chromosomes. 

 18-19. Winter egg, metaphase of segmentation spindles, 18 chromosomes. 



Saranac zvillozv aphid. 



20 a and b. First spermatocyte, prophase, showing double series of 10 chro- 

 mosomes. 



21. First spermatocyte, prophase. 



22. Paired chromosomes from prophase of first spermatocyte. 



23. First spermatocyte, metaphase. 



24. First spermatocyte, anaphase. 



25. A pair of second spermatocytes. 



26. Young spermatid. 



Harpszuell zvilloiv aphid. 



27. Parthenogenetic egg, metaphase of maturation spindle. 

 28-29. Parthenogenetic egg, prophases of segmentation mitosis. 



