306 Delf. — Studies of Protoplasmic Permeability by 
a great deal in length, ultimately 37 per cent., but did not alter appreciably 
in diameter. At intervals of two hours the lengths of the half-cylinders were 
measured, and the amount of shrinkage in mm. is recorded (loc. cit., p 184). 
In Fig. 17 the data are presented in graphic form, the dots being the 
original data and the broken lines joining them being an attempt to recon- 
struct the course of the curves over the gaps in the record. In this form the 
results can be easily compared with the curves set out in *;the body of this 
paper. 
Fig. 16. Relation of temperature and permeability of protoplasm. 
From F. van Rysselberghe (loc. cit., p. 190). 
It will be seen that/as is to be expected, each curve begins with a more 
rapid fall, and the rate of plasmolysis gradually declines to zero when the 
shrinkage is complete at the pith-length of 7 2 mm. F01 the low tempcia- 
tures the ends of the curves are beyond the twenty-four hours at which the 
records cease, while for the high temperatures the contraction is practically 
complete when the first record is taken at two hours. The fiist matter 
for criticism is van Rysselberghe s method of exti acting a tempei atui e- 
relation from these data. He takes what may be called a vertical section 
of the chart ; that is to say, the amount of contraction shown by the respec- 
tive curves at two hours of time is adopted, the latios being those set out on 
p. 305. Now it should be clear that the only vertical comparison of the 
curves which has any real signi ficance is the impossible one that should be 
taken an instant of time only after the beginning. As each cui ve begins 
with the same big osmotic pressure force (the difference of concentration of 
