CHANGES IN REPRODUCTIVE CELLS OF ELASMOBRANCHS. 291 
31. About this time the intra-zonal fibrils spread out, until 
those from either pole meet at the circumference of the cell 
(fig. 49), and at these somewhat angular connections there ap- 
pear beaded thickenings in the threads, which (fig. 50, 0.2.) 
stain and thus form an interesting stepping-stone between 
Flemming’s intermediate bodies and a true cell-plate. 
32. At the same time the chromatic rings gradually lose their 
original connection with the outer spindle-fibres (0.s., fig. 52), 
which begin to bulge out and to pass round the nuclei towards 
the poles (fig. 53). The chromatic rings are thus cast loose 
in a surrounding fluid vacuole, but the inner core of fibres 
(fig. 52, 7. s.) continues to pass through them. 
The bulging out of the intra-zonal fibres round the nuclei is 
marked by a collapse at the point of their original distension 
at the equator (figs. 51, 52, 53), which brings the outer and 
the inner sheath together in the median plane (figs. 52, 53). 
Thus the central portion of the residual spindle figure presents 
the appearance of a sharply differentiated fusiform body be- 
tween the cells (figs. 53, 54, 55). Across its middle there is a 
chromatic band, produced by the fusion of the intermediate 
bodies (figs. 63, 54, 55, 56, 57, b.i.). 
While contemplating the changes I have just described, it is 
impossible to avoid the impression that the rupture of the outer 
spindle-sheath and the consequent outflowing of the enclosed 
fluid to form the nuclear vacuoles (figs. 54, 55, 56, n. v.), are 
the primary causes by which the expanded equatorial spindle- 
figure is made to collapse, and that it may also have a direct 
mechanical connection with the formation of the primary con- 
striction between the daughter-cells. 
33. As in the divisions of the first spermatic period, the spheres 
(fig. 37, a) begin now to travel over the surface of the nucleus, 
generally along a groove (n. g., fig. 54) like that described in 
§ 15, towards its equatorial face.! 
34. The expanded central portion of the spindle remnant 
now lies between the daughter-cells (which are otherwise quite 
1 *Arch. fiir mikr, Anat.,’ Bd. xhii, p. 423; cf. M. Haidenhain, op. cit., 
Taf. xxv (figs. 14, 21, 22, 23). 
