CHANGES IN REPRODUCTIVE CELLS OF ELASMOBRANCHS. 283 
thin chromatic floor. In consequence of this, the spheres 
(fig. 27, a. b.) appear to occupy the hollow of a little nuclear 
cup, and by the continuance of this filling-up process the 
remnant of the inner spindle-core is pushed gradually to one 
side, and eventually out of the nucleus altogether, but it con- 
tinues to pass round the nucleus (in a more or less deep furrow) 
(fig. 27 a, n.g.) towards the spheres. 
16. The course of the terminal spindle-filaments becomes 
generally coincident with the surface of the vacuole about 
each nucleus, and they consequently take a curved course from 
each end of the fusiform remains of the original spindle-figure 
(between the cells) to the spheres in the polar faces of the 
nuclei. So that the whole arrangement. of the daughter-nuclei 
and spindle-fibres at this time bears (see fig. 27 a) a curious 
resemblance to the figures seen in the divisions of the micro- 
nucleus! during the conjugation of many infusoria. 
17. The chromatin in the daughter-nuclei now blows up 
once more into a foam, and eventually completely fills the 
vacuoles originally surrounding them (figs. 28, 29, 30) while a 
nucleolus appears in the reticulum of each, generally at the 
base of the shallow depression (mg., fig. 29), which persists as 
the remains of the nuclear cup described above (§ 15). This 
depression, together with the spheres, is gradually rotated 
somewhat to the equatorial side (as in fig. 29), and the chromatic 
granules existing in the cytoplasm, becoming fewer in number 
and larger in size, assume the characters of the chromatic 
bodies described by Hermann in the spermatogenesis of Mam- 
malia (fig. 30, 0. ¢.). 
18. The cells are now practically at rest once more, but 
the fusiform spindle remnant, with its equatorial band of 
intermediate bodies (fig. 30, 6. 7.), continues long after the 
daughter-cells have come to rest, and eventually degenerates 
and vanishes in the equatorial plane. 
Mitoses of the above description are carried out with hardly 
any variation in their details, through all the cellular divisions 
' See Maupas, “‘ Le Rajeunissement Karyogamique chez les Ciliés,” ‘Arch, 
de Zool.,’ exp. tm. vii, 1889 (pl. ix, figs. 14—20). 
