Nuclear Division in Lilium Martagon. By E. SarganL 285 
incomplete, that is, it does not extend from end to end of the 
chromosome. The ends Z, l, remain undivided. If we imagine the 
limb of each segment following the course of the spindle fibres as 
indicated by the arrows in fig. 45, A, and at the same time the fission 
along b , b } opening out, it is clear that each segment becomes V- 
shaped by a partial fission, and without any elaborate curving. Such 
figures as the chromosomes drawn in fig. 46, a and b, are readily and 
simply explained by this hypothesis. I am convinced, however, 
that the forms assumed by the chromosomes in earlier stages are 
inconsistent with it. 
I cannot hope here to do more than give a short account of my 
own view, and indicate the nature of the evidence which supports it. 
Fig. 47 . Fig. 48 . 
The large number of spindle figures examined may conveniently be 
divided into three classes, distinguished by the shape of their 
chromosomes. 
1. The limb of each chromosome occupies less than a quarter of 
its whole length. 
2. The limb is between a quarter and half the whole length of 
the chromosome. 
3. The length of the limb is more than half the whole length of 
the chromosome. 
1. This class includes three types (fig. 47) : chromosomes with 
limbs which curve inwards with reference to the whole spindle figure 
(a), chromosomes with straight limbs (5), and with outcurving limbs 
( c ). In 100 chromosomes at this stage I counted 53 with incurved 
limbs, 33 with straight limbs, and 14 with outcurved limbs. 
2. The three types reappear in this class (fig. 48), but their 
comparative frequency is rather different. In 100 chromosomes the 
limbs of 52 were incurved, 30 outcurved, and 18 straight. That is, 
; while the proportion of chromosomes with incurved limbs to the whole 
is about the same as in the earlier stage, the outcurved limbs have 
increased in number at the expense of the straight ones. This is 
easily understood when we consider that in the case of the chromosome 
with incurved limb the surface in contact with the spindle fibres was 
originally the outer surface of the chromosome (fig. 47 a), while those 
with straight and outcurved limbs adhere by the surface formed by 
