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 



