Allen, — Nile l ear Division in the 
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it usually extends the full length of the daughter chromosome, excepting 
at its polar end. Fig. 73 represents the only instance I have found in 
which an early stage of the split was visible. In this case a fission appears 
in the middle portion of one daughter chromosome, the equatorial end still 
showing no evidence of division. This fission of the daughter chromosomes 
is usually in a plane which passes through the chromosome and the central 
axis of the spindle ; it would seem, therefore, to represent a split at right 
angles to the original one which produced the daughter chromosomes. 
But on account of the twisting and untwisting which the chromosomes have 
undergone, it is impossible to be certain upon this point. 
The newly separated granddaughter chromosomes immediately diverge 
at their equatorial ends, giving to each daughter chromosome the form of 
a V, with the apex toward the pole. All four equatorial ends of the V are 
usually turned outward (Figs. 74, 75, 77) ; in Fig. 77 the chromosomes are 
shown as seen from the interior of the spindle, the equatorial ends then 
being turned away from the observer. Fig. 76 shows an unusual case, in 
that the two V’s lie in planes perpendicular to each other ; the four 
equatorial ends are in this case also turned outward. The upper daughter 
chromosome in this figure shows some evidence of being split throughout 
its length, the polar end being apparently double. 
As the V-shaped daughter chromosomes finally separate from each 
other and approach the poles of the spindle (Figs. 79, 88), they commonly 
contract more or less, losing the long-drawn-out appearance which they 
have frequently presented during the process of separation, and regaining 
about the same length that they had in the equatorial plate. 
It is not uncommon for single chromosomes to remain attached in the 
equatorial plane, even after their fellows have reached, or nearly reached, 
the poles. Fig. 78 represents two V-shaped daughter chromosomes which 
have undergone longitudinal splitting ; one arm of one has separated from 
the corresponding arm of the other, but the remaining two arms are still 
in contact, and indeed are so closely attached as to appear fused. In this 
case the angles of the V’s have been pulled nearly to the poles of the 
spindle. A similar case is shown in Fig. 58. These are instances of the 
possibility of a fusion, or apparent fusion, between two separate portions 
of the chromosome substance when closely appressed — a possibility which 
was illustrated in an earlier stage by the occasional fusion of the daughter 
chromosomes at their ends. It is not surprising that such a fusion of two 
masses of this very plastic substance should occur ; the striking fact is 
rather that it occurs so seldom. That in such cases there is no real fusion, 
but only a temporary adhesion, is suggested by the history of the chromo- 
somes, which, in the nucleus of the animal sperm, form a seemingly 
homogeneous mass, but which reappear as separate entities before the 
fusion of the sexual nuclei. 
