140 
J. Bret land Farmer. 
can only be settled by extensive and comparative observation, and 
as soon as anyone embarks on the perilous path of interpretation 
he is beset by risks that ever await the pioneer. 
Certain guiding principles, however, are slowly emerging from 
the chaos, and the ancillary sciences of chemistry and physics are 
now more helpful than formerly. Much has been done to eluci¬ 
date the behaviour of colloids, and we possess a clearer knowledge 
of the energy changes that are associated with the chemical and 
physical transformations within the cells, and we also realise that 
dimensional considerations are not to be ignored in estimating the 
effects of forces which are acting within the limits of a single cell. 
It may be freely admitted that we are certainly not in a 
position to furnish anything like a full and satisfactory explanation 
of the features which characterise the progress of a nuclear division. 
But if we are to wait until we can offer a full solution of the problems 
involved, we may as well abandon the enquiry at once. We are 
obviously bound to go on, and therefore any serious attempt to 
frame even a working hypothesis, to say nothing of a complete 
explanation, is entitled to consideration. 
Dr. Lawson, in two memoirs published by the Royal Society 
of Edinburgh,' has attempted an extensive explanation of, at 
any rate, some of the problems of mitosis, and it is the purpose 
of this communication to endeavour to weigh the merits of his 
contribution. The earlier memoir mainly deals with the stage 
known as synapsis, and Dr. Lawson feels himself justified in con¬ 
cluding that the common impression is that this stage is associated 
by a contraction of the chromatin is erroneous, but that the signi¬ 
ficance of the stage is open to more reasonable interpretation, viz., 
that the nucleus is greatly enlarging and is acting as a sap vacuole. 
Dealing in the first place with the view that the generally 
admitted idea of contraction is erroneous, it is not improbable that 
many workers will continue to find some difficulty in accepting Dr. 
Lawson’s conclusions, and it must be confessed that he has not, on 
his side, rendered agreement too easy. 
A critical study of his own figures convincingly proves that, 
even in the object selected by Dr. Lawson himself, a contraction 
of the chromatin-containing mass clearly occurs during synapsis. 
This is shown by the method of tracing, and also by calculation 
1 The phase of the nucleus known synapsis, Trans. Roy. Hoc. Ed., 
Vol. XLVII, p. 591, 1911. 
Nuclear Osmosis as a factor in mitosis. Trans. Roy. Hoc. Ed., 
Vol. XLVIII, p. 137, 1911. 
