The Somatic Mitoses in Hyacinthus orientalis var. albulus. 
373 
seen which gives any Support to this view; Fig. 22 shows a polar view with 
16 chromosomes arranged in 8 pairs, with diagranmiatic clearness, but 
this is the orily case which was found among a large number of polar 
views, of which Figs. 23, 24 are good average types. Düring the course 
of the mitosis no indication of any pairing was observed, although in 
a few cases a certain similaritv of shape might be used to group the chromo- 
somes into couples. 
On the whole, the facts observed in Hyacinthus lead one to the con- 
clusion that a paired arrangement of the chromosomes forms no essential 
part of the normal mitotic figure. It may well happen that occasionally 
an arrangement may occur which is more than usually suggestive of 
“pairing”, for it is not improbable that chromosomes which are similar 
in shape may, nnder the same conditions, act in similar fashion, and 
thus lead to an apparent pairing, but this seems to be all that is justified 
by the majority of figures. 
As regards the difference in the length of the chromosomes very 
little evidence can be offered which is to be regarded as conclusive. 
The phenomenon has been recorded in Galtonia (Digby TO), and in 
Yucca and other forms (Müller ’10, T2); but so far as Hyacinthus is 
concerned, although the chromosomes do sometimes appear to be of 
different lengths, this has so often been found to be only a result of fore- 
shortening, that one hesitates to attach much importance to it. There 
is also to be considered the elastic nature of the chromosomes which is 
so obvious in this species, which makes it very probable that the chromo- 
somes differ in size and shape during mitosis, according to the amount 
of stress to which they are subjected, and the position in which tliey 
are with regard to such forces. 
The longitudinal fission. 
There is now no lack of evidence that some form, of alveolization 
of the daughter chromosomes takes place in the telophase, and such a 
phenomenon has been recorded by Gregoire and Wygaerts (’04) in 
Trillium, by Gregoire (’06) and Merrevian (’04) in Allium, by Digby 
(TO) in Galtonia and by Fraser and Snell (’ll) and Sharp (’13) in 
Vicia. As regards the interpretation of this vacuolization there are 
however two possibilities — the one to regard it as the foreshadowing 
of the longitudinal fission which will finally be accomplished in the next 
mitosis — the other as an indefinite loosening out of the substance of 
the chromosome, with no end other than the distribution of the chromatin 
over the nuclear area. 
