578 STUDIES IN GENERAL PHYSIOLOGY 
experiments in order to find out whether there was a division 
of the nucleus without a segmentation of the protoplasm, 
and whether this division was mitotic. Norman found that 
by carefully selecting the concentration of the sea-water a 
division of the nucleus without a segmentation of the proto- 
plasm occurred, and, moreover, that the division was mitotic.! 
The number of cells into which the egg divides at once when 
brought back into normal sea-water is often larger than the 
number of the nuclei preformed in the concentrated sea- 
water. It therefore seems as if a further division of the 
nuclear matter occurs immediately after the eggs are put 
back into normal sea-water. The addition of sodium chlo- 
ride seemed to injure the eggs, and I asked Mr. Norman to 
try the effects of other chlorides. He found that an increase 
in the concentration of sea-water by the addition of MgCl, 
is less harmful than that of any other chloride. 
It seems to me that it is necessary to discriminate in these 
experiments between two different effects produced by the 
addition of salts (or the increase of the concentration of sea- 
water). The one effect is that produced on the nucleus and 
consists of a destruction (liquefaction?) of the nuclear mem- 
brane, and possibly a dissolution of the substance which 
binds the chromosomes together. This effect seems within 
certain limits to increase with the concentration of the sea- 
water. The other effect consists in the gradual suppression 
of the motility of the protoplasm. This may possibly be 
due to a decrease in the fluidity of the protoplasm (water 
rigor). This effect also becomes stronger with the increase 
in the concentration of the sea-water. Ata certain point in 
the increase of the concentration the nuclear membrane will 
be dissolved and the chromosomes scattered (through proto- 
plasmic motions), while the protoplasm is no longer able to 
undergo segmentation. This was observed by Norman. If 
1W. W. Norman, Archiv fiir Entwickelungsmechanik, Vol. III (1896), p. 106. 
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