Nuclear Osmosis and Meiosis. 
23 
Professor Lawson appears to think I have misrepresented him 
in my remark as to his use of the term permeable membrane in 
connection with the alleged osmotic process. He says “The term 
I have continually used throughout the paper is a permeable plas¬ 
matic membrane” (the italics are his own). In the first place, on 
turning to the paper itself (Nuclear osmosis, p. 144) I find the 
following statement:— 
“ Everything necessary to promote osmotic diffusion is present, 
there is a permeable membrane and substances of different 
chemical composition and presumably of different density 
on either side of it. It is therefore not difficult to under¬ 
stand the gradual diminution of the karyolymph, as shown 
in these figures, on the basis of osmotic diffusion. The 
karyolymph has passed out into the cytoplasm by exos¬ 
mosis.” 
Will Professor Lawson, in the face of this quotation, still 
maintain that 1 have misrepresented him ? 
In the second place, even if we waive the question as to the 
exact nature of the nuclear membrane, and agree to call it a plas¬ 
matic one, this is still not ad rem in so far as an osmotic process is 
concerned. It is not with the plasmatic character, but with the 
osmotic property of the membrane that we have to do. A permeable 
plasmatic membrane would be about as effective in the matter as a 
permeable or perforated bladder. Semi-permeability (or selective 
permeability) is, of course, one of the essential conditions in the 
absence of which no osmotic pressure could be either set up or 
maintained. Is it possible that Professor Lawson himself is not 
clear as to the difference between osmotic and ordinary diffusion 
processes? If so his description of chromatin as “an osmotically 
active substance ” at a time when it “ is undergoing a change to a 
more condensed form ” (Study in chromosome reduction, p. 604) 
becomes explicable though it still remains unintelligible. 
If, however, Professor Lawson means by exosmosis or“ osmotic 
diffusion ” of the karyolymph a mere diffusion of nuclear sap from 
the nucleus into the cytoplasm, consequent on the abolition of the 
semi-permeable character of the plasmatic nuclear membrane which 
was hitherto responsible for the maintenance of nuclear turgor, 
then any contraction of the latter will depend solely on the surface 
tension properties of this nuclear membrane. The whole achromatic 
spindle, supposed to arise through the distortion of the cytoplasmic 
reticulum which is assumed to be coherent with the membrane, 
must then be attributed to the effects of surface tension alone. 
But this aspect of the problem seems to have escaped him altogether, 
or at any rate it has not been discussed. And in the absence of 
evidence to the contrary we may be permitted to doubt whether 
the surface tension of the nuclear membrane under the prevailing 
conditions would be competent either to produce or to effect such a 
distribution of strain as would account, in any way whatever, for 
the origin and peculiar characters of the achromatic spindle. 
But Professor Lawson appears to desire to have his cake and 
eat it— i.e., to postulate a membrane endowed with qualities enabling 
it to permit of loss through diffusion outwards (exosmosis) while at 
the same time it is maintaining an osmotic pressure within; for he 
speaks of the chromatin as an “ osmotically active substance ” as 
