174 L. B. WALLACE. 



ipheral position, are connected by linin fibers to one pole only, 

 and are drawn to this pole before the daughter V-shaped chromo- 

 somes are more than half way to their destination (PI. I., Figs. 

 23- 24). 



According to Wagner --" bei der ersten spermatocyten- 

 theilung theilt sich der Nucleolus entweder in der Ebene der 

 Aquatorialplatte mit den Chromosomen zusammen oder auszer- 

 halb denselben neben einem der spindelpole." In the latter case 

 he believes it to be cast out into the cytoplasm. Here, as else- 

 where, what he considers to be a " Nucleolus " is without doubt 

 the pair of accessory chromosomes which often lie closely 

 apposed to one another and arrive at one pole before the other 

 chromosomes. Their eccentricity of position might mislead one 

 into thinking that they are being thrown out of the nucleus. 



In every case where a section is found cutting through the 

 equatorial plate of the primary spermatocytic monaster trans- 

 versely, cross-sections are found of the nineteen double V-shaped 

 chromosomes and frequently are found also the accessory chromo- 

 somes which appear larger because of their oblique position in 

 relation to the spindle axis. Their nearness to the cell-wall is 

 here quite clearly demonstrated (PI. I., Figs. 21, 22). During 

 the telophase the nineteen V-shaped chromosomes enter into a 

 partial rest, becoming granular but not forming a reticulum, 

 while the accessory chromosomes in one of every two daughter 

 nuclei stand out in a striking manner as two densely stained rods 

 against the granular background and in sections stained with 

 Hermann's method, their affinity for the safranin at a time when 

 the other chromosomes take the gentian violet, makes them still 

 more prominent (PI. I., Fig. 25). 



The nuclear membrane now forms, one nucleus containing a 

 pair of accessory chromosomes, the other none (PI. I., Fig. 26), 

 and the V-shaped daughter chromosomes, attached by their apices 

 are quickly drawn into the equator of the spindle for the second 

 maturation division (PI. I., Fig. 27). Frequently the cell body 

 of the primary spermatocyte does not undergo division until 

 toward the close of the telophase of the second maturation 

 division. 



