bo 
STRUCTURE OF CERTAIN CHROMOSOMES 5 
taking place at any time; but there is evidence that each of 
these threads represents an entire limb of the anaphase V 
from which it is derived ; and that their parallelism in pairs is 
brought about by the folding together of the two 
limbs of that V. This evidence is contained in the following 
considerations. 
In the daughter-star of the anaphase the chromosomes are 
indubitably V-shaped, with equal limbs diverging to an angle 
of some 45 degrees,’ figs. 3 and 5 (the apparent shortness of 
some of the limbs in these figures, and the apparent hook shape, 
is due partly to unequal degrees of contraction, partly to fore- 
shortening). But as the star passes into the clump stage this 
divergence becomes less pronounced, and in the completed 
clump we find no such open V’s, but in their place a bundle of 
short straight staves, figs, 29 to 33, each of which shows the two 
thin chromatic threads mentioned above. The observer’s first 
impression naturally is that each of these staves represents 
one limb of a V, the relation of this one to the other being 
masked by the crowding of the elements. But consideration 
shows that this can hardly be. For the staves are only present 
in a far smaller number than the limbs of the anaphase V’s— 
in the completed clump in only half that of the limbs. Take 
for instance fig. 29. This clump, a very early one, contaims, as 
I make it, thirty-two seeming staves, of which twenty-nine 
are shown in the drawing. Now the anaphases of Salaman- 
dra atra, from which this is taken, have twenty-four V’s, 
therefore forty-eight limbs. Manifestly, therefore, not all the 
staves of the clump can represent single imbs ; but some of 
them must represent entire chromosomes. Let us suppose that 
sixteen of them are in this case ; then these will account for 
thirty-two limbs ; and the remaining sixteen staves will represent 
sixteen single imbs, thus making up the required tale of forty- 
eight. Now take fig. 80, a completed clump. I make out 
twenty staves shown fairly distinctly (not all drawn), and the 
unanalysable portions of the clump may account for a very 
1 This for the nuclei of the Amphibia. As we shall see, it is not the case 
for those of all groups of animals. 
