The Structure of certain Chromosomes and the 
Mechanism of their Division. 
By 
Arthur Bolles Lee, Hon. F.R.M.S. 
With Plates 1 and 2. 
Part I. Srructurs. 
(a) Historical. 
THE first suggestion of any structure at all observable in chro- 
mosomes seems to be due to Pfitzner (‘ Morph. Jahrb.’, vii, 
1882), who suggested that a chromosome is made up of a row of 
sranules of chromatin embedded in an achromatic or less 
chromatic thread. Belief in these granules—later dignified by 
the names of ‘ chromomeres’, ‘ chromioles’, and the like—long 
held sway, and still lingers in many minds. I do not think it 
necessary to enter into a detailed discussion of this view ; for 
I think it is now indubitable that the supposed granules are 
nothing but the misinterpreted images of twists of the chromo- 
some, or of bulges in it. The figures illustrating this paper 
afford abundant instances of bulges caused by twists of the 
chromosomes ; and those illustrating my paper on the chromo- 
somes of Paris quadrifolia (‘La Cellule’, xxvii, 2, 
1912, p. 265) of bulges caused by alveoles in them ; either 
of which, if indistinctly seen, may lend themselves to an 
erroneous interpretation as granules." 
At the present time two other theories are in the field: the 
chromonema theory, and the alveolation theory. 
1 The chromomere theory seems to have been given up even by Fl em- 
ming, who at one time accepted it. For in his paper, ‘‘ Neue Beitrage zur 
Kenntniss der Zelle’’, II. Th. (‘Arch. mikr. Anat.’, xxxvii, 1891), whilst dis- 
cussing the division of chromosomes, no mention is made of the granules, 
which he had formerly taken to be active agents of the division ; and his 
figures no longer show any such granules, but in many places show instead 
more than hints of the bulges of a twisted thread. 
NO, 257 B 
