24 



DESCRIPTION OF PLATES. 



Plate II. 



Harpszocll luillotu aphid. 



Fig. 30. Parthenogenetic egg, resting nuclei, showing nucleolus divided before 

 mitosis. 

 31-32. First spermatocyte, metaphase. 

 33-34. First spermatocyte, anaphase. 



35. Second spermatocyte, prophase. 



Aphis oenotherae. 



36. First spermatocyte, metaphase. 



37. Second spermatocyte, metaphase. 



Oenothera aphid, No. II. 



38. Parthenogenetic egg, metaphase of maturation spindle. 

 39-40. First spermatocyte, metaphase. 



41. First spermatocyte, early anaphase. 



42. First spermatocyte, late anaphase. 



43. Young spermatid. 



Black milkzueed aphid. 



44. Parthenogenetic egg, metaphase of maturation spindle. 



45. Parthenogenetic egg, 4-cell stage, metaphase of segmentation spindle. 



46. Spermatogonium, prophase of mitosis. 



47. First spermatocyte, metaphase. 

 48-49. First spermatocyte, anaphase. 

 50-51. Second spermatocyte, anaphase. 



Orange milkweed aphid. 



52-53. Parthenogenetic egg, metaphase of maturation spindle. 



54. Parthenogenetic egg, metaphase of maturation spindle, showing the 



two largest chromosomes united (1 + 1). 



55. Young oocyte, showing plasmosome (p) and six of the chromosomes. 



56. Parthenogenetic egg, 16-cell stage, prophase of mitosis. 



57. Parthenogenetic egg, polar body {p. b.) and three segmentation spindles. 



