A HISTORY OF BEDFORDSHIRE 
vernacular name as the title of a book at once wonderfully learned and 
lucid, has shown how this common, clean and hardy species can be 
made as it were a compendium of all zoology; how the consideration of 
its structure and vital powers, its birth and breeding, its distribution and 
alliances will lead the inquiring disciple onward step by step through all 
the philosophy of life. For those who are content to learn from it the 
general plan which with endless modifications runs through crabs, lob- 
sters, shrimps, woodlice and all the other Malacostraca, there is scarcely 
a species more convenient than the crayfish. Its stalked eyes, its two 
pairs of antennae, its lips, stomach and intestine, its carapace, the six 
pairs of jaws, its five pairs of trunk-legs, its jointed pleon and the pleo- 
pods, its tail-fan, and within the body the liver-like gland, the heart, the 
brain and ventral nerve-chain, and all the arrangement of the muscles 
are easy for the most part to distinguish in specimens prepared for the 
table or otherwise preserved. Its behaviour alive in the aquarium is not 
without interest. The shedding of the skin, known as ecdysis or exuvia- 
tion, is worth observing by those who can secure the chance. Those 
who can study the creature in its native haunts have ever the opportunity 
not only of amusing themselves, but of instructing others. For of any 
complex living organism all the efforts of all the zoologists can seldom 
or never so exhaust the interest that true lovers of nature need despair 
of discovering some new charm or wonder in the creature or its ways. 
The sessile-eyed Malacostraca are constructed on the same general 
plan as the stalk-eyed Decapoda or ten-footed crustaceans, to the macru- 
ran or long-tailed division of which the crayfishes belong. In some full- 
grown crabs and in some larval forms of lobster-like and shrimp-like 
species the stalked eyes attain a quite exorbitant length. With respect 
to the crabs, it is true, the epithet may not quite literally apply, because 
the orbits are usually as long as the eyes ; but when these stilted organs 
are raised out of their sockets they present a remarkable appearance. In 
the crayfish however, as in the common crab, there is no great length of 
stalk to attract attention, and therefore little regard is in general paid to 
the substantial difference in ophthalmic structure which separates such 
forms from the Isopoda and Amphipoda. These latter groups have the 
eyes seated in the head, without stalks either long or short. They are 
not ten-footed, but fourteen-footed. Their branchial or respiratory 
apparatus is not, as in crabs and shrimps, concealed by the carapace. 
Their size in all the British land and freshwater species is limited to a 
low standard. In their general appearance the fondest admirer would 
scarcely claim any high degree of dignity and grace. They are not by 
any means warmly esteemed, except by those who have learned to appre- 
ciate modest merit and neglected virtue. Man the omnivorous does not 
even pay them the compliment of eating them, though there is little 
doubt that they all have a good shrimp-like flavour. But in spite of all 
prejudices on our part and dissimilarities on theirs, and in the teeth of 
such contemptuous designations as woodlice, slaters and pill-bugs, the 
terrestrial Isopoda are as truly malacostracan crustacea as the lobster and 
92 
