786 Kemp.—On the Question of the Occurrence of 
mass, which must, from the nature of its formation, contain twice the normal 
number of chromosomes. With recovery of the tissue from the action of the 
drug, these tetraploid cells increase considerably in size, and further, divide 
mitotically and so form two daughter nuclei, also with the tetraploid chromo¬ 
some number. The fact that the number of these tetraploid nuclei near the 
growing point is seen to be diminished at the later periods of the experiment, 
together with that of the occurrence of numerous large multinuclear cells and 
others with two diaster figures, appears to show that the tetraploid nuclei 
eventually break up. This they may do either while in rest or during 
division, and so form smaller nuclei with the normal diploid number of 
chromosomes, or something approximating to it. That they tend finally 
to disintegrate entirely is indicated by the fact that a gradual series can be 
traced from the above multinuclear cells, to some which are completely 
shrivelled and contain merely distorted masses of chromatin. A difficulty 
in estimating the effect of the chloral hydrate upon a particular root con¬ 
sists in the fact of the secondary nature of the structural modifications 
resulting from the action of the drug ; which modifications would otherwise 
afford the readiest means for such an estimation. The number of the 
binuclear or tetraploid cells visible after partial recovery and further growth 
of the tissue is no real gauge of the extent of the action, but is dependent 
upon the number of nuclei in actual process of division during the im¬ 
mersion of the root in the poison. Again, the position of a tetraploid cell 
after a period of subsequent growth is largely dependent upon that of the 
dividing cell from which it originated, and therefore is not a very definite 
datum in determining its history, or at least its rate of division. The real 
nature of the action of the chloral hydrate upon the tissue remains doubtful. 
That it affects the chromatin itself appears from the fact that, at the earlier 
fixations, the whole nucleus looks finely granular and somewhat abnormal, 
taking the stain feebly; and the chromosomes also are granular and appear 
to be slightly swollen. It is possible that the disappearance of the achro¬ 
matic fibres is due not to the action of the poison upon any definite fibrillar 
structure as such, but to a modification of the chemico-physical relations 
normally existing between chromatin and cytoplasm ; a modification 
arising secondarily, and as a result of the action of the chloral hydrate upon 
the chromatin itself. 
Examination of Figs, i and 17 reveals certain interesting features in 
the relation to each other of the nuclei contained in the tetraploid cells. 
In roots examined directly after removal from the poison, or after a short 
period of subsequent growth, these nuclei, which, as described above, are 
abnormally granular, with badly defined membranes, are seen to lie close 
together in the cytoplasm. They do not seem to exert any mutual 
attraction and their contiguous sides are flattened. They look indeed as 
if crushed together ; a condition ascribed by Strasburger to the action of 
