298 DR THOMAS H. BRYCE ON 
leucocytes. The longitudinal splitting takes place early. The Vs are unequal, with 
one short and one long leg. The latter in the metaphase is of such length that 
when all seen in one section it extends round a third of the circumference of the 
cell. This makes the metaphase figures so complicated that I cannot be certain of 
the number of chromosomes. 
In the late anaphases the chromosomes are merged again into a seemingly solid 
mass of chromatin, which no amount of extraction will resolve into separate elements, 
The long tails are gradually drawn into the common mass and an oval solid nucleus 
is formed. In many resting cells, as mentioned above, the nucleus has the same 
character, and the appearances point to the coarse reticular stage being reached by 
a sort of vacuolation. Throughout all the phases the chromatin retains the staining 
reactions described for the resting nucleus. 
(4) History of the Achromatic Figure. 
At the stage at which we left the centrosomes when they lay close together, 
and the corpuscle has rounded up for division, we noticed that there were no direct 
connecting threads between them. On their outer sides the radiations are strong 
and join the general reticulum. As the centrosomes draw apart (Plate I. fig. 9) it 
becomes clear that there are still no fibres directly joming the centrosomes, and 
that the radiations are stronger on the side of the nucleus. Both at the equator of the 
spindle figure and where the radiations of the asters meet, the fibres seem to branch and 
anastomose. I think the appearances are in favour of an anastomosis rather than of a 
mere crossing of the fibres; one never sees a loose end at any stage of the process. 
When both centrosomes are sharply in focus at the same time, the axis of the 
spindle system is seen to be occupied only by a faint system of branching and 
anastomosing fibrillee. 
There is, strictly speaking, no ‘central spindle’ spun out between the centrosomes, — 
but only two systems, mainly of mantle fibres, which join one another round the equator 
(Pl. I. figs. 11,12). In a cross section of the metaphase figure there is no core of fibres 
representing a cross-cut central spindle in the heart of the equatorial crown ; only a few 
fine fibrillze are to be made out. ; 
The appearances point, not to any new formation of radiating fibres, but to a con- 
version, step by step, of the general network into radiating tracts, until it has all been 
drawn into the opposing systems, and the achromatic figure comes to be placed sym- 
metrically in the corpuscle. 
As the daughter chromosomes move apart, the axis of the spindle system is seen to 
be occupied by loosely-arranged, irregularly-disposed fibres; and as the anaphase pro- 
gresses, the ‘subequatorial fibres’ (Mmves) come out more and more clearly, while 
the axial system becomes more loosely arranged (PI. IT. figs. 13, 14,15; Pl. V. fig. 39), 
until we have a central space traversed by coarse much-branched fibres, and bounded 
SSS 
