M5 
Helve l la crisp a, Fries. 
As the nucleus passes out of contraction the thread is gradually 
unwound from either pole (Fig. 13), and in the spireme it is impossible 
to distinguish the two portions. The thread is distributed over the whole 
of the nuclear area, and indications of a longitudinal duplication become 
visible (Figs. 17, 18). The thread is very granular, and on the appearance 
of the duplication the granules are observed to lie in pairs (Fig. 18). 
Eventually the thread appears double throughout its length (Fig. 19). 
The second contraction is not very marked ; a certain amount of 
aggregation of the nuclear thread towards one side of the nucleus takes 
place, but it is rather a change in position than in length (Fig. 20). Very 
little actual contraction of the thread occurs, but the longitudinal fission is 
temporarily obliterated. Soon the thread loosens out again, the split 
reappears, and the thread is arranged in irregular loops, in each of which 
the split is often very evident (Fig. 21). 
The spireme next breaks up to form four gemini, the limbs of which 
still show the longitudinal fission (Fig. 22). The limbs may be twisted 
together or remain divergent, and the chromosomes gradually contract into 
the typical heterotype forms, a figure 8 and an incompletely closed 8 being 
the commonest (Fig. 23). The tendency is, however, for the chromosomes 
to remain long and thin while they are free in the nuclear area. The final 
contraction occurs at about the time when the chromosomes pass on to the 
spindle (Figs. 24, 25, 26). 
As the chromosomes begin to contract the nuclear membrane becomes 
less distinct, although the nuclear area is clearly evident throughout the 
division. The astral rays are quite distinct and spread round the nuclear 
area and out into the dense cytoplasm surrounding it (Figs. 24, 27). 
The mature chromosomes are typically V-shaped, and in most the 
fission is obliterated (Fig. 26), but in some it is indicated by a cleft in each 
limb (Fig. 25). The limbs separate from each other so that each bivalent 
chromosome is divided transversely, and at this stage some of the daughter 
chromosomes are V-shaped, owing to the reappearance of the split (Fig. 27). 
As they pass towards the poles the chromosomes become much elongated 
(Fig. 28), contracting again as they reach the poles (Fig. 29). 
On the reconstitution of the daughter nuclei distinct chromosomes are 
no longer visible, the whole chromatic substance forming a network (Fig. 30). 
On the spindle of the second division four chromosomes reappear, each 
of which is V-shaped by incomplete fission. In most cases they are attached 
at the apex of the V, and here the final separation of the limbs occurs 
(PL XIX, Figs. 31, 32). The chromosomes may elongate during their 
passage to the poles, or they may remain as more or less rounded bodies. 
The resulting four nuclei enter upon a short resting stage. 
