LIMA HIANS AND ITS MODE OF LIFE. 221 
there is no evidence of its being able to turn in the nest. A third 
and equally important function which this organ has to perform 
is the spinning of the threads with which to bind together the 
material of which the nest is constructed. Occasionally the 
animal may be observed to apply the tip of the foot for a short 
time to some object lying near, and when it is drawn off a fine 
thread will be observed to have become attached, and thereafter 
spun out to be fixed somewhere else in the burrow. By constant 
repetition of this process, the burrow is at last lined with a sort of 
feltwork, and the parts are bound so closely together as to require 
some force to pull them apart. 
As we stated, the animal is not particular as to what material it 
may thus bind together. It is not even at a loss when there is 
lack of material with which to build, for it then constructs an 
ingenious lattice-work of its own byssus threads. This is well 
illustrated in a specimen kept by Mr. M‘Crie, now for six months, 
which has built a sort of awning of its threads to increase its 
household accommodation. 
The second important organ in Lima is the mantle. The primary 
function of this organ in all Molluscs is the secretion of the shell, 
under which it lies as a thin layer of tissue. This is often the sole 
function of the mantle, which usually comes the length of the 
edge of the shell, but does not project beyond it except to form a 
siphon or suction-tube. But in the case of Lima the fact that there 
is this little possibility of communication with the outside world 
has led to wonderful specialization in the form of a complicated 
sensory organ adapted to its mode of life. The edges of the 
mantle have given rise to a great number of filamentous tentacles 
which project in every direction, giving the whole animal the 
appearance of a regular Caput Meduse. These snake-like tentacles 
usually also exhibit a constant twisting and waving motion, and 
project occasionally far out from the nest through the little aper- 
tures left in the feltwork of byssus threads, 
Various observations have been made as to the properties of these 
remarkable tentacles. Thus they sometimes adhere to the finger, 
or anything applied to them, so firmly that the animal may thus 
be dragged through the water in the aquarium (Robertson), They 
will even break off sometimes, by what seems to be a voluntary 
throwing off, rather than be detached from the object to which 
they adhere. Thus tentacles or parts of tentacles may be occa- 
