A 4 DORIS L. MACKINNON. 
the nucleus grows at the expense of the cytoplasm, while, 
during periods of rest, the cytoplasm exerts a “reducing ” 
influence on the nuclear mass, bringing it back to its normal 
proportions. Hertwig sees in the maintenance of a certain 
definite proportional relation between nucleus and cytoplasm, 
fixed for each kind of cell, an absolute essential for the con- 
tinuance of healthy cell-life. Anything that disturbs the 
equilibrium unduly, such as long continued feeding (when 
the nuclear element becomes abnormally enlarged), or star- 
vation (when shrinkage of the cytoplasm is the disturbing 
factor), produces an injurious state of things that will result 
in death to the cell, if it be not corrected by nuclear reduc-_ 
tion, and a consequent return to normal proportions. Consider 
the conditions used artificially to produce encystation— 
abundant nourishment, followed by complete starvation. 
Nothing could be more favourable to a great nuclear 
preponderance, and for this state of ‘‘depression”’ the organ- 
ism seeks a remedy in encystation. As the nuclear growth 
had previously been excessive, so now the “reducing ” power 
of the cytoplasm comes into play to an equally abnormal 
degree. Ninety-five per cent. of the orginal nuclei are 
“ absorbed,” and still further reduction is effected by subse- 
quent formation of polar bodies. 
In the cold culture in my experiment an undue proportion of » 
nuclei survived the eliminating process, and, further, they 
were markedly rich in chromatin. A lowered temperature 
may be considered to have an inhibiting effect on nuclear 
reduction. This is probably also the cause of the relative 
slowness of the early stages in the cold culture. In the cold, 
nuclear reduction is slow and incomplete. 
But there is every reason to believe, from the experiments 
of Hertwig and his students, that the ‘“ Kern-plasma Rela- 
tion ” is lowered or raised by the altering of the temperature 
conditions to which the cell is subjected. What would be 
excess of nuclear mass at a high temperature might not be in 
the least unfavourable to further development at low tem- 
perature. i 
