144 
“Nuclear Osmosis .” 
faced with difficulties of, if possible, a still higher order. For whence 
comes the high degree of concentration of osmotically active 
substance, and why does it not make itself apparent in many other 
obvious ways, as for example, in a great increase in the size of the 
cell, which should occur at any rate in animal cells with their 
tenuous membranes ? Dr. Lawson notes that it is a curious 
circumstance that somatic mitoses are characterised by “ the 
drawing out of only two conical shaped sheaves of kinoplasm ” 
instead of the multipolar arrangement that often marks the early 
stages in the meiotic spindles. He attributes the difference to the 
absence of vacuoles in the cytoplasm of cells in the meiotic phase, 
and to their presence in the ordinary body cells; “The numerous 
vacuoles which are always present in the cytoplasm would render a 
radial or a multipolar arrangement of the kinoplasm impossible.” 
But he does not attempt to explain the cause of the impossibility, 
nor is it at all self-evident. Vacuoles are not rigid, immovable 
things, but in any event one would rather have expected that if they 
were able to exercise any mechanical influence on spindle formation 
at all, they would rather have tended to produce than to check the 
formation of multipolar spindles, inasmuch as they do serve in 
some degree to partition up the cytoplasm. 
As regards the stages of anaphase and telophase the author 
has not worked out the consequences of his ideas in any detail so 
they need not be further discussed here. Enough has perhaps been 
already said to indicate that in the opinion of the present writer 
a case has not been made out for the acceptance, even as a 
working hypothesis, of “ nuclear osmosis ” as a serious factor in 
mitosis ; and certainly not in the sense that Dr. Lawson claims for 
it. Any far reaching theory must be applicable to the animal as 
well as the plant cell, for the essential similarity of the process in 
the two kingdoms is even more striking when the differences in 
other respects between the respective cellular conditions are borne 
in mind. 
