Vines —Proteolytic Enzyme of Nepenthes (///). 567 
readily penetrated into the glands whilst the epidermal cells 
stained but slowly. This differentiation was still more marked 
when methylene-blue was introduced into the pitcher together 
with some albumin, in which case the colouration was seen to 
extend into the tissues beyond the glands. At the same time 
the cytoplasm of the glands showed marked aggregation. 
It appears, therefore, that the glands not only secrete the 
digestive fluid, but are also the agents in absorption. 
I should have been glad had it been possible for me to do 
no more than to express my appreciation of so much valuable 
work in a subject which has long interested me, to confirm 
the accuracy of the observations, and to recognize the validity 
of the conclusions. There are, however, certain points con- 
nected with Clautriau’s experiments in vitro upon which I am 
reluctantly compelled to join issue. 
In the first place, I take exception to his inference that the 
addition of HC1 to the pitcher-liquid, as practised by other 
observers, is useless. It is perfectly true that if the pitcher- 
liquid be naturally acid, it will digest proteid without any 
addition of HC1. I have frequently found this to be the 
case : but I have also found that if a small quantity of HC1 
or an organic acid, such as citric, be added, digestion proceeds 
very much more rapidly, so that instead of extending over 
days, as did Clautriau’s experiments, a few hours suffice. 
Moreover, neutral pitcher-liquid will not digest at all. 
Furthermore, the experiment upon which Clautriau bases this 
opinion is inconclusive, because no observations were made 
to determine the relative rate of digestion of the albumin in 
tubes A and B : had this been done, it is probable that the 
albumin in the acidified tube B would have been found to 
disappear some time before that in tube A. 
Secondly, with regard to the doubt which Clautriau ex- 
presses as to the presence of the enzyme in the liquid of 
unopened pitchers, my experience entirely confirms the ac- 
curacy of the statement made by von Gorup-Besanez that 
this liquid is very active when properly acidified. 
But the really important divergence between Clautriau’s 
