550 Dr. M. Hartog. [Dec. 1, 
either end. These arise as a sort of radiation around the nucleus, extending 
from the whole of its periphery into the cytoplasm: the radial fibres come to 
approximate at their distal ends into bundles tapered at their ends, and 
ultimately in this way coalesce into the single spindle. The disceding 
daughter chromosomes join up at the ends of the spindles to form the 
daughter nuclei. When cell division does not follow nuclear division, as in the 
embryo-sac and in the pollen-formation of Exogens, etc., the daughter nuclei 
remain for some time joined up by spindles. 
Thus the peculiar phenomena of osmosis and growth of the Metazoan 
centrospheres can shed no light on the nature of the forces at work in the 
spindle itself, resulting in the discession of the chromosomal segments; since 
the latter phenomena are repeated in Plants, which have no centrospheres. 
le 
The problem of the character of the forces involved has been before my 
mind for at least twelve years, and resolved itself into the investigation of the 
physical laws according to which the cell behaved in respect of the dumb-bell 
and spindle figure. I tried hard to induce friends expert in physics to take 
up the study of cytology for this purpose; but in vain. The publication in 
1902 of a remarkable essay by Gallardo, summarising and extending the 
arguments on behalf of the views to which I leant, and including experiments 
more or less on the lines of those I had planned, showed how necessary 
was detailed work on these lines, and how much remained to be done. I 
found also that the physical text-books and original papers, to which my own 
reading and the hints of my friends had led me, did not deal with the special 
problems involved: notably differences of “permeability” in the cytoplasm, 
and the redistribution of substances in a heterogeneous mixture under 
the action of a centred force to which the medium was not uniformly 
permeable; while the necessary conception of “ material’chains of force” had 
not yet been even formulated by physicists. 
I therefore commenced last autumn a series of experiments with models 
in methodical continuation of haphazard essays dating at least half a dozen 
years back. I have received much valuable criticism (for the most part 
destructive of my crude ideas) from many physical friends, and notably my 
colleague, Professor Bergin, M.A., and helpful guidance in matters both 
theoretical and practical, from my son-in-law, Mr. William Cramp, A.M.LE.E. 
The photographs that illustrate this paper have been taken immediately 
under my direction by Mr. H. C. Booth, except fig. 5, which I took myself. 
