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 antenna?, 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
