A HISTORY OF SURREY telson, with others less easy to observe in the branchiae, that is, the series of respiratory organs which are concealed under the protection of the carapace. In 1893 the Rev. James Menzies read a paper on 'The Natural History of the Crayfish ' before the Holmesdale Natural History Club, Reigate. In the published abstract he does not record any Surrey locality for crayfishes, but he says, ' It has been observed that they have a preference for those parts of the river which run north and south, because of the shade from the midday sun,' and as to their diet he observes, ' Larva? of insects, water-snails, tadpoles, or frogs which come within reach are suddenly seized and devoured, and it is averred that the water rat even is liable to the same fate.' 1 Of the terrestrial Isopoda known as English, Surrey is likely to possess as many as any other county, and though the species hitherto recorded are not numerous they include some that are rather specially worthy of notice. These crustaceans, better known under the con- temptuous name of woodlice, are Malacostraca like the crayfish, but of a lower grade and with many differences. Their eyes are sessile in the head, instead of being placed on jointed pedicels. Their breathing organs instead of being in the front part are in the caudal division of the animal's body. Their trunk-feet are fourteen in number instead of only ten. Moreover, these seven pairs of legs are severally attached to seven movable body segments without the overarching shield or carapace to which the corresponding segments are tied in crabs, lobsters and the like. With all these marks of distinctness it may seem odd and fanciful to classify a crab and a woodlouse in the same group. But there is another aspect from which this grouping may be viewed. Throughout the Malacostraca, miscellaneous as they may seem, it is possible to trace uniformity alike in the number of body segments and in the number of paired appendages belonging to those segments each to each. Merely to count the pieces and the pairs, it is true, might be misleading, for though the segments and the limbs never exceed a certain stipulated number, they very frequently fall short of it. There are sometimes segments without appendages, and sometimes appendages which do not seem to belong to specially allotted segments. A wide comparison however soon makes it clear that missing appendages have been relin- quished only because they had become useless or inconvenient, and that reduction in the apparent number of body segments is due to advanta- geous consolidation. Even thus qualified the uniformity is so striking that few minds can resist the inference from it that all the Malacostraca are derived from common ancestors and may therefore naturally be grouped together, as apart from other animals which cannot pass this particular test. In the same way when the appendages are considered, whether in the endless diversity of genera and species or as a series exhibited in a single animal, it might at the first view seem a mockery to refer them to any common original. Antennae, mouth-organs, 1 Holmesdale Natural History Club Proceedings, p. 18 (1893). 1 88
