22 DESCRIPTION OF PLATES. 



PLATE II. 

 Stenopelntatus. 



FIGS. 46-47. Nuclei of spermatogonia, showing 2 and 3 nucleoli (M). 



48-49. Prophase of spermatogonial mitosis, showing two exceptionally large 



chromosomes of equal length. 



50. Equatorial plate of spermatogonial mitosis, 46 chromosomes. 

 51-54. Spermatocytes in spireme stage, nucleus containing a nucleolus (n), 

 and a chromatin element (.*), which is attached to one end of 

 spireme and gradually increases in size during growth stage of 

 Spermatocytes. 



55. Spireme longitudinally split and showing the beginning of cross for- 



mation. 



56. Spireme segmented, tetrads forming. 



57. One split segment and a part of another connected by bands of linin. 



58. More open cross and diamond forms ; element x conspicuous. 

 59-60. More contracted cross and diamond-shaped tetrads ; linin bands shown 



in 60, where element x is also present. 



61. Different forms assumed by element x during tetrad stage (figs. 56-60) 

 62-63. Diamond-shaped and contracted cross-shaped tetrads from metaphase 

 of first maturation mitosis, showing linin connections. 



64. Diamond-shaped tetrad with spindle-fibers attached; a-a, probably 



halves of one univalent chromosome ; b-b, halves of the other. 



65. Dyad from anaphase of first maturation mitosis. 



66-67. Metaphase of first maturation spindle, showing element x in different 



positions. 



68. Late anaphase of same. 



69-70. Equatorial plate of first maturation spindle, 23 chromosomes and ele- 

 ment x below, in fig. 69. 



71. Chromatin massed at poles of spindle; element x isolated at one pole. 

 72-73. Two resting Spermatocytes of the second order, one containing ele- 

 ment x, the other not 

 74-76. Successive stages of breaking down of element x. 



77. Prophase of second division; dyads evident, but no sign of x in this 



or following stages. 



78. Second spermatocyte division metakinesis. 



79. Same ; late anaphase. 



