336 Annals Entomological Society of America __[Vol. VII, 
Since the substances of this colloidal or emulsified solution have 
a tendency to collect at surfaces and when once out of solution 
(according to Loeb (81) are very difficult to bring into their 
former condition, permanent, more or less impermeable bars 
to the process of metabolism may be set up. These may be 
broken down by a change in the chemical process or a change 
even in their rate, due to exterior causes of temperature or food 
quantity. 
Childs in some experiments on Planarians finds that the 
toxicity of alcohol which he uses as a measure of the rate of 
metabolism varies inversely with the age of the animal, i. e., 
metabolic processes are being lowered and katabolism is gaining 
the upper hand. He finds however, that rejuvenation is pos- 
sible by a change in the rate of these metabolic processes. 
Since metabolic processes are carried on through alveolar 
walls of phases in the protoplasm of the cell and since the 
longer this process of metabolism is carried on at the same rate 
and in the same chemical nature, the more permanent these 
walls become, a lowering of metabolic processes, i. e., senes- 
cence due to the establishment of alveolar walls which have 
through their permanency become bars to the action of metabo- 
lism, is the result. He finds however, that a change in these 
processes will result in an increased rate being possible for them. 
If an animal is starved for a short time and then fed, its ability 
to withstand the alcohol is greatly increased—this can be 
explained by the probability that the processes have gone on 
in spite of the lack of food and that the actual accumulation of 
cytoplasmic alveolar walls of obstruction have been destroyed 
and the cell thus brought into a younger stage of differentiation. 
If the animal is starved for only a few days, this increased 
resistance is very small, upon again refeeding. 
The rejuvenation has not gone on to as great an extent, 
therefore the resistance is less than that of the animal starved 
for a longer time. A similar result is obtained with animals 
that have been forced to regenerate parts—the larger the piece 
is that has been regenerated, the greater the increase in resist- 
ance to alcohol. In the case of regeneration, direct visible data 
has been given by Godlewski (19) showing that regeneration 
actually leads to a simplification of cells and a reverse process 
of cytomorphosis that Minot did not take into consideration in 
