THE HERMIT-CRAB. 317 
and are generally found covered by the single valve of a shell, 
which they also hold in its position by their claws, and thus carry 
about with them a shield. 
Mr. Spencer Bate put into a glass of water some sea-fleas, 
along with some green ulva; he was surprised to find that in a 
couple of hours the little creatures had rolled the sea-weed into a 
tube, in which they were safely and peacefully housed, thrusting 
their head and antennz out of the end of their sea-weed pipe. 
The Amphithoe rubricata seeks under stones, or in the crevices 
of rocks, or among the stems of the fuci, a sheltered spot where 
it constructs a nest, which is composed of a silky material, and 
when examined under the microscope appears to be woven most 
delicately, while here and there through the fabric run thicker 
threads, often spiral. 
PINNOTHERES VETERUM. 
The Pinnotheres veterum is a pretty, bright, rose-coloured crus- 
tacean about the size of a pea; he takes up his lodging in the shell 
of an oyster, and lives on terms of the closest intimacy with the 
aristocratic bivalve. Pliny believed that the grateful crab returned 
the hospitality of the oyster by lending the blind mollusk the 
use of his eyes. Whenever a danger threatened, the guest pulled 
the mantle of his host; at the signal the valves were shut, and 
both the oyster and his friend placed in perfect security. Plutarch, 
however, estimated the services which the pinnotheres rendered 
the oyster differently. He says that the tiny crab acts as a 
watchman, and when a little fish comes within the valves of the 
mollusk, which are always open, the crab pinches the oyster, 
which immediately closes its shell, and entraps the fish. The 
prey thus secured, the pair then consume at their leisure. It is 
needless to say that this is not the truth. The presence of the 
pinnotheres in the shell of the oyster, is entirely due to the instinct 
of self-preservation. This timorous little crustacean is found not 
