5 86 
Balls . — Temperature and Growth. 
(h) The decrease in growth-rate at constant temperature is also pro- 
portional to the amount oi‘ x } which is present in the cell. 
Until these assumptions have been proved or disproved the following 
presentment has no direct value. 
Let us start by imagining that some substance, or group of substances 
(probably situate in the nucleus) is, as it were, the governor which controls 
Curve 6. The components of the curve of growth. Varying temperature. 
the constructive metabolism of the cell. For convenience in discussion we 
will again have recourse to a symbol, and denote this governor by G. 
We know that the body ' x' is excreted as a result of the growth- 
process, and that its excretion ceases with the cessation of growth, and that 
it exerts an injurious effect upon the process — -that is to say, upon G. 
This effect is presumably chemical, and will be affected by rise of 
temperature. 
