CRUSTACEANS 



Gammarus pulex (Linn.), to which Dr. Hamilton calls attention in a 

 passage already quoted. Less economically useful but scientifically of 

 more interest are the * well-shrimps.' These may be regarded as the one 

 redeeming feature in the niggardly annals of Berkshire carcinology, for 

 though the earliest discovery of them was made in another part of 

 England, it was through Berkshire specimens that they were first recog- 

 nized as a determinate part of our English fauna. Bate and Westwood, 

 in their History of the British Sessile-eyed Crustacea^ when discussing the 

 genus Niphargus^ Schiodte, write as follows : 



Between the years 1835 and 1842, Koch, in the continuation of Panzer's great 

 work on the Insects of Germany, published descriptions and figures of two species which 

 he procured from the draw-wells of Ratisbonne and ZweibrUcken, under the single 

 name of Gammarus puteanus. In 1851 Schiodte obtained other specimens from the 

 caves of Carniola ; and to him is due the credit of establishing this interesting genus 

 among the Amphipod Crustacea. In the year 1852 Prof. Westwood was so fortunate 

 as to obtain from a pump with a substratum of clay, near Maidenhead, a quantity of 

 these animals. 1 



The specimens forwarded to Prof. Westwood from Maidenhead 

 proved to belong to the species Niphargus agui/ex, Schiodte, and this, 

 which is possibly but by no means certainly identical with Gammarus 

 subterraneus, Leach, 1813, was soon afterwards found to occur in the 

 wells of several counties. 8 



That all the Malacostraca are tied and bound together in singularly 

 close relationship is not readily apparent to those ' that choose by show, 

 not learning more than the fond eye doth teach.' The eye must be not 

 ' fond ' in the old sense of simple and foolish, but well informed, before 

 it can perceive the resemblances that connect the groups together, or even 

 duly appreciate the features that keep them distinct. The Amphipoda 

 to which Gammarus and Niphargus alike belong have as a rule all the 

 same parts and appendages as the shrimp of commerce, with one excep- 

 tion. The eatable shrimp, like the crayfish and the crab, has pedunculate 

 eyes. According to the length of the stalk, the depth of the orbit, and 

 other arrangements, movable organs of vision are capable of playing a 

 great part in the activities and appearance of species which possess them. 

 But this does not affect the Amphipoda, all of which have the eyes 

 sessile. They cannot, like a poet in a fine frenzy, roll them to and fro, 

 nor like a decapod abruptly lift or lower them. These unjointed eyes 

 cannot take rank in the series of appendages, and accordingly they cannot 

 be supposed to imply a supporting body-segment. In the head and 

 thorax of an amphipod therefore there is no proof of more than thirteen 

 segments, and the last seven of these are not covered by a carapace or 

 immovably consolidated. By the intervention of a flexible membrane 

 they are after a fashion articulated one to the other, with the same 

 freedom of movement as that which pertains to the segments of the 

 abdomen both here and in the lobsters and true shrimps. Of the limbs 

 corresponding to the seven segments of the thorax or perason, the first two 



1 Brit. Sess. Crust, pt. 7 (1862), i. 312. * Loc. cit. p. 317. 



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