24 J • Bretland Farmer. 
effective at a time when, on his own showing, karyolymph is passing 
out of the nucleus. 
I am further charged with having, in my review, passed over 
“ The discovery of the stages showing the persistence of the nuclear 
membrane throughout the prophase ” (loc. cit., p. 617). I am not 
quite clear wherein the discovery consists. If the alleged closing in 
of the membrane over the chromosomes and its partition over their 
several individual surfaces is meant, I would remark that 1 did refer 
to this, and with a scepticism which Dr. Lawson’s reply has done 
nothing to allay. If, however, something else is intended I would 
point out that it has long been known that the nuclear membrane 
may persist throughout the prophase and even on to the metaphase 
of mitosis. Such an example is afforded by Fucus, which I think 
would be a difficult case in many respects to reconcile with Professor 
Lawson’s hypothesis ; and there are others besides. 
It is also alleged that I omitted to mention “ Three important 
phases of mitosis ” of which it is suggested that the hypothesis of 
nuclear osmosis offers “ A fair and rational explanation.” (i) the 
origin and formation of the achromatic fibrils, (ii) the attachment 
of the fibrils to the chromosomes, (iii) the movements associated 
with the resolution of the multipolar figures into a bipolar arrange¬ 
ment (loc. cit., pp. 616—617). I am at a loss to understand this, 
because as regards (i) and (ii) I expressly pointed out what 
appeared to me to be some of the obstacles in the way of 
accepting the proposed explanation. It seemed to me, and seems 
so still, that the “ explanation ” introduces new difficulties without 
explaining any of the old ones. I may add that the suggested mode 
of transition from the multipolar to the bipolar position indicated 
by Dr. Lawson appears to invoke purely gratuitous assumptions as 
to properties and behaviour of a reticulum under the postulated 
conditions of strain. I regret that Professor Lawson should 
apparently have overlooked my remarks on the aforesaid matters, 
for he is apparently quite unaware of the number of points in which 
his hypothesis bristles with difficulties. It is of little use to speak 
of “convincing proofs,” “irresistible conclusions” or even of 
“belief” to those who feel, as I do, that the arguments are 
fallacious and the conclusions are unsound. 
The treatment accorded to the origin and behaviour of the 
interzonal spindle (i.e., between the two daughter-nuclei during the 
anaphase) is another example of the way in which awkward points 
are shelved. The whole development, contour, extension towards 
the peripheral cell-wall, and especially the appearance and position 
of the cell-plate, should have all been considered in connection with 
any comprehensive theory of the mechanics of mitosis. It is not 
enough to invoke hypothetical relaxation of the fibres, nor to be 
assured that there “ is no doubt ” in the author’s mind that:— 
“ These threads represent the same state of tension expressed 
in the achromatic figure of the later prophase and meta¬ 
phase. The lines of tension have merely shifted with the 
movements of the chromosomes.” 
A passage of this sort suggests a lack of appreciation of the 
fundamental distinction between a mere expression of opinion and 
a scientific reasoned argument. 
A series of facts, with which the author has not as yet dealt, 
