678 TRANSACTIONS OF SECTION K. 
evidence of physical disturbances of an electrical nature which accompany, and 
indeed in a measure determine, the course of mitosis. This is indicated, not only by 
the movements that proceed within the nucleus, and concern the linin and chromo- 
somes, but also by the remarkable alterations in surface-tension exhibited by the 
nuclear membrane. 
It is well known that at a certain stage of the heterotype division, for example, 
the chromosomes move to the periphery of the nucleus, and each one is removed 
as far as possible from every other chromosome. At this stage, to which Haecker 
has given the name of ‘diakinesis,’ the nucleus reaches its maximal size. 
Diakinesis is not the only stage in which there is an indication of repulsion 
between the elements of the chromatic linin. Measurements prove that all such 
periods of repulsion are also marked by an increase of nuclear size which is 
transitory, and either disappears or alters in a synchronous fashion with them, 
These phases of enlargement have generally been regarded as directly connected 
with the intake of liquid by the nucleus, due to a hypothetical change in osmotic 
conditions. But, so far as I am aware, no satisfactory explanation has yet been 
given as to why, or how, the supposed increase of osmotically active molecules 
within the assumed semi-permeable nuclear membrane could be effected. On the 
other hand, an enlargement of the surface-membrane of the nucleus would 
necessarily follow on the migration towards it of chromosomes or other bodies 
carrying similar electrical charges. For the induced charge in the particles of 
the membrane would of course weaken its coherence, and for the same reason that 
the free chromosomes repel and move away from one another. 
There is evidence to show that the proteins are able to carry such charges, and 
this is a matter of the highest importance as affording a clue to many other 
processes in which changes of surface-tension play a part, besides those connected 
with nuclear division. 
Not the least of the many remarkable properties exhibited by the proteins lies 
in their capacity of taking on either a positive or a negative charge of electricity. A 
clear proof of this was afforded by the beautiful experiments of Billitzer, who showed 
that, when so charged, the colloid moves as a whole towards one pole or the other 
on sending a current through the liquid in which it was suspended. At first sight 
it may not be easy to understand how it is possible for a colloid to receive and 
retain a charge under the conditions which obtain either in the solution or in the 
cell. It must, however, be remembered that the liquid contains electrolytes in 
solution also, and any disturbance in the equilibrium of the products of ionic 
dissociation will be accompanied by corresponding differences of potential. The 
most reasonable explanation of the phenomenon in question seems to be that the 
colloids are unequally permeable to the ions, whereby there comes to be a 
preponderance of one or the other group associated with the proteins. Perhaps 
this should be connected with the remarkable though still imperfectly understood 
property of adsorption which is characteristic of many colloids. 
Much, however, still remains to be done before a complete survey of the 
electrical changes that are associated with mitosis can be made. We especially 
desire more complete information on the nature of the chemical processes which 
are involved. For it is obvious that the physical changes must ultimately be 
connected with the transformation of materials which goes on so energetically at 
these recurrent periods of nuclear activity. We do not yet know how or why the 
chromosomes that have been dispersed at diakinesis should again congregate on 
the spindle prior to their final separation. Possibly this is to be connected with 
the signs of disturbance in the extra-nuclear cytoplasm, which in its turn finds 
expression in the differentiation of the achromatic spindle. The character of 
this body has long aroused the suspicion that its existence is to be attributed to 
electrical causes. The more recent work serves to indicate that this suspicion 
was well founded. 
The more complete study of the chemistry and physics of karyokinesis is certain 
to prove valuable for another reason. The successive changes which the nuclei 
of both animals and plants exhibit when they are undergoing division are so 
remarkably similar that it seems exceedingly probable that the processes actually 
a 
