402 E. R. Downing, 
lying in a short axis. The shape then changes, this minor axis 
becoming the major axis (Fig. 49). The irregularly beaded thread 
becomes a spiral coiled about the major nuclear axis on the nuclear 
wall, and making there three complete turns (Fig. 51). Again the 
nucleus changes shape, becoming a flattened sphere and the spireme 
thread so shifts that its segments become meridional. Fig. 53 and 
54 show pole views. The nuclear membrane now disappears. The 
spireme fragments at the poles, forming six segments, each con- 
taining four chromomeres (Fig. 55). 
Equatorial plate. 
These segments contract, forming six spherical chromosomes, in 
the equatorial plate. Meantime the centrosomes have appeared at 
the poles and each chromosome is connected with the centrosome or 
through it with the cell wall by a fibre (Fig. 56). 
Metaphase. 
As the metaphase begins the spherical chromosomes are elong- 
ated (Fig. 57). At division two chromomeres go into each daughter 
chromosome. It seems probable therefore that this is a reduction 
division. Interzonal fibres connect the chromosomes as they pull 
apart and during this anaphase the central spindle fibres were de- 
tected (Fig. 58). The usual appearance of the chromomeres in the 
late telephase is evident here. 
The spermatid. 
The spermatid immediately after the separation of the daughter 
cells of the spermatocyte division is spherical, but there is a pro- 
jecting point of protoplasm on one side frequently, marking its con- 
nection with the sister cell (Fig. 60). Let us call the diameter 
passing through this projection and through the centrosome the polar 
diameter. The nucleus is now biscuit-shaped (Fig. 59 and 60). In 
pole view it appears circular in outline, in side view plano-convex. 
There follows the same change of shape in the spermatid that was 
noted in the spermatocytes at this stage. The cell becomes an 
elongate polyhedron, the nucleus an ellipsoid of revolution. Their 
long axes coincide and lie in the direction of the polar axis which 
becomes therefore the major axis of the spermatid. It would of 
course be possible for the cell to elongate at right angles to the 
polar axis; the centrosome would lie in a minor axis. It might then 
