ii2 LIFE AND HER CHILDREN. 
themselves. As soon as they grow a little accus- 
tomed to the place they will begin feeling about with 
their foot to find a spot, and then pressing the tip 
firmly against it, will draw it back after a time, 
leaving a thread behind. The huge fan-mussel or 
Pinna, common off Plymouth, forms threads so silky 
that they have actually been woven into gloves. 
The mussel then has the power of spinning new 
threads and settling in new spots, but he is prac- 
tically a stationary animal, providing himself with 
plenty of food by the rapid motion of his fringed 
gills, so that even young shrimps in spite of all their 
efforts are carried into the whirlpool. Then when 
the tide goes down, he closes his shell, shutting in 
enough water to last till the sea returns, and it is 
while he is left high and dry that the sea-birds often 
wrench him from the rocks and devour him. 
In the scallop (S, Fig. 42) we get a step farther ; 
for though he too forms a slight cable and anchors 
himself to the rock, yet he can in most cases with- 
draw it at will and dart through the water in long 
rapid leaps, so that a group of young scallops look 
as if they were performing a dance. Mr. Gosse, who 
watched this in an aquarium, saw the scallop draw as 
much water as it could hold within its mantle, and 
then, closing the edge, squirt it out at one corner so 
as to drive itself along in the opposite direction. The 
lima, which is nearly related to the scallop, and has a 
lovely orange fringe to its mantle, often builds a nest 
with its threads, working in pieces of coral, gravel, 
and shells, and fastens it to the seaweed, lining it 
with a smooth layer of slime, and taking refuge in it 
out of the way of crabs and fishes. But the scallop 
