50 LIVERPOOL BIOLOGICAL SOCIETY. 
with various species, and I have no doubt his results will 
be laid before us on some future occasion. 
EXPERIMENTS ON MoLuuscs. 
Scattered over the rocks at Puffin Island, above high- 
water mark, and above any of the sea-weeds, in the region 
of the little incrusting Lichina pygmea, the region which 
Vaillant has called the subterrestrial or zero zone, we find 
numerous specimens of the small periwinkle Littorina 
rudis, and it is difficult to see how this mollusc manages 
to live, and why it has migrated so far up the shore. It feeds 
upon the lichen, and is very sluggish in its habits, often 
remaining for days—perhaps months—without moving 
from the one spot. Like its relations further down the 
shore, it is a branchiferous mollusc fitted for breathing in 
water, and yet we find it living and apparently flourishing 
in the air: possibly it may be in process by becoming 
adapted to a terrestrial mode of life. We know that some 
of these molluscs can shut themselves up in their shells so 
tightly as not to allow any water to pass in or out. Gosse 
has told how Purpura lapillus is able in this way to 
withstand the action of fresh water for eighteen hours. 
This may help us to understand how it is that some 
marine molluscs upon the rocks are not injured by 
drenching showers of rain, but it will scarcely solve the 
difficulty in regard to the specimens of Littorina which 
stick to the dry rock for many days, unless they have 
become adapted to breath in air, and some experiments 
which I have made render it probable that this modi- 
fication has taken place. 
I collected some specimens from the rocks above high- 
water mark, and after keeping them perfectly dry in a 
cardboard box in the laboratory for six days, during which 
time they showed no signs of life, I put ten of them into a 
tc Soho pe. 
