135 
Amongst the mollusca useful to man we may in- 
stance those which supply food, as oysters, the large 
snails, fattened for the table in Germany, cockles, 
and limpets: those which yield treasures for com- 
merce, as corals and pearls: those which yield a small 
contribution to clothing, as the silk of the pinna. 
Of vermes the gordius is said to have a poisonous 
bite producing inflammation: the furia of Bothnia 
to be fatal when it penetrates the skin. ‘The leech 
is well known as a useful auxiliary to the surgeon. 
Dr. Shaw says, the soft holothurie, which float oc- 
casionally on calm seas, have the power of causing 
great inflammation of the skin of those by whom 
they are incautiously handled. The medusz, which 
abound in all seas, possess generally a stinging qua- 
lity, which has obtained for them the name of sea- 
nettles. Even mollusca are not exempt from para- 
sitic mollusca. The cuttle-fish has its internal worms, 
the fasciole loliginis; the earthworm, its ascaris 
lumbrici. 
From the crustacea we may select lobsters and 
prawns as supplying to man agreeable repasts: scor- 
pions and spiders as injurious by their venom. Crabs 
and prawns are the prey of onisci; and perhaps most 
others either of teeniz ascarides, or echinorynchi. 
Of insects, whole tribes are eminently useful to 
man. I need only mention the silkworm, the cater- 
pillar of the bombyx mori, originally from the north- 
ern provinces of China. In the days of the emperor 
Justinian, Greek missionaries are said to have brought 
the eggs concealed in reeds from India to Constan- 
K 4 
