Malacostraca this is the only representative likely to be found living, in a wild or natural state, in the county. In all epochs of human history this and its kindred species have probably been consumed in large quantities for food. In the present epoch they are consumed in large quantities for education. Their fitness for this purpose should not be disregarded. Everything nowadays has to submit to analysis or dissec- tion or both, water and milk, stars and ether, history and law, plants and animals. Among the latter enthusiastic students make their choice, some taking delight in the viscera of a kitten or the brains of a baboon, others preferring the minute anatomy of a slow-worm or a slug. Very likely all these subjects, according to taste or whatever the appreciative sense may be, are delectable handling and alluring to look at. But for unsophisticated persons, not yet prejudiced in favour of a snail or a cuttle or a sea-sausage, one can honestly commend the class of Crustacea as a basis and beginning of anatomical practice. Within that class the river crayfish supplies the very model of a handy specimen, not clumsy like a lobster, not inconveniently small like a shrimp, and withal so de- cent and decorous, internally and externally so free from anything to cause disgust, that the student may with satisfaction begin his study by eating a large part of his lesson book. For even when the meat or muscular part has been consumed the external skeleton remains, not un- instructive. All through the wonderfully diversified orders and sub- orders of the Malacostraca the fundamental character of that skeleton is found persistent. In some great sections of the group the species have their eyes set on movable stalks. In other great sections they have them seated immovably in the head. But interlacing characters make it difficult to draw a sharp line between these two assemblages. Apart from the eyes there are normally nineteen pairs of appendages in all the Malacostraca, each pair having theoretically a segment of the body to which it is attached, while the body ends in a segment which has no dis- tinct appendages. The eyes are followed by two pairs of antennas or feelers, a pair of mandibles usually stout or sharp for biting or piercing, two pairs of maxillae thin and flat, and then a pair of jaws called maxilli- peds because they are sometimes foot-like. After these come either two more pairs of maxillipeds and five pairs of legs, or else a complete series of legs in seven pairs. But the so-called legs are seldom all of them fitted for walking. The terminal portion of the animal known as the tail, the abdomen, the pleon or swimming part, carries six pairs of ap- pendages, some of them called pleopods or swimming feet and some uropods or tail-feet, but under whatever names they pass subject to much diversity in form and function. From the Decapoda or ten-footed divi- sion Huxley selected ' the crayfish ' as the subject of a lucid and concise zoological treatise. His explanations however are not limited to a page or a paragraph, but expanded into a volume, and in its chapters those who live where crayfishes live will amply learn what excellent opportunities for mental improvement that companionship affords them.
For specimens of Buckinghamshire sessile-eyed crustaceans I am
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