130 Darwin, and after Darwin. 
form of a wreath (D), and subsequently (by the breaking of 
the loops formed by the fibres) in the form of a star (E). A 
further movement within the nucleus leads to an arrangement of 
the broken loops in two groups (F), the position of the open ends 
of the broken loops being reversed as compared with what pre- 
viously obtained. Now the two groups diverge, and in many 
cases a striated appearance of the achromatin substance between 
the two groups of chromatin loops is observable (H). In some 
cases (especially egg-cells) this striated arrangement of the 
achromatin is then termed a ‘‘nucleus-spindle,” and the group of 
chromatin loops (G, a) is known as “the equatorial plate.” At each 
end of the nucleus-spindle in these cases there is often seen a 
star consisting of granules belonging to the general protoplasm 
of the cell (G, c). These are known as “ polar stars.” After the 
separation of the two sets of loops (H) the protoplasm of the 
general substance of the cell becomes constricted, and division 
occurs, so as to include a group of chromatin loops in each of the 
two fission products. Each of these then rearranges itself to- 
gether with the associated chromatin into a nucleus such as was 
present in the mother cell to commence with (1)1. 
Since the above was published, however, further 
progress has been made. In particular it has been 
found that the chromatin fibres pass from phase D 
to phase F by a process of longitudinal splitting (Fig. 
37 g,h; Fig. 38, VI, ViII)—which is a point of great 
importance for Weismann’'s theory of heredity,—and 
that the protoplasm outside the nucleus seems to 
take as important a part in the karyokinetic process 
as does the nuclear substance. For the so-called 
“ attraction-spheres” (Fig. 38 II a, III, III a, VIII to 
XII), which were at first supposed to be of subordinate 
importance in the process as a whole, are now known 
to take an exceedingly active part in it (see especially 
IX to XI). Lastly, it may be added that there is a 
1 Ray Lankester, Zvcyclop. Brit., 9th ed., Vol. XIX, pp. 832-3. 
