CHAPTER XXIII 



THE CRAYFISH— AST ACUS FLUVIATILIS 



Apus cancriformis affords so good an example of the leading 

 features of crustacean anatomy that it will not be necessary to 

 enter into minute details of the anatomy of the crayfish, the 

 more so because this species is fully described in Marshall 

 and Hurst's "Practical Zoology," and is the subject of an 

 admirable memoir by the late Professor Huxley, a book which 

 should by all means be read by young zoologists. They will 

 find in it a full and interesting account of the habits and 

 structure of crayfishes, as well as a description of the different 

 species of crayfishes and their distribution in different parts of 

 the globe. 



The common river crayfish is found in many rivers of 

 England, particularly in those which flow through chalk- or 

 limestone districts and have a good deal of lime dissolved in 

 their waters. It lives in holes which it burrows in the river 

 banks, in the mouths of which it lies in wait for its prey. It 

 is a voracious and indiscriminate feeder ; almost any kind of 

 flesh is acceptable to it, and it is able by means of its powerful 

 pincers to overcome animals considerably larger than itself. 

 Some years ago it was very abundant in the Thames and Cher- 

 well, and was the subject of a regular fishery, for its flesh is 

 esteemed a greater delicacy even than that of the prawn or 

 lobster. But in 1887 there was a pest among the crayfishes in 

 the Upper Thames and its tributaries ; they died in great 

 numbers, and so few survived that the fishery became un- 

 profitable and has practically ceased to exist. In recent 

 years the number of crayfishes has increased, and they 

 are common enough in some small tributaries of the 

 Thames, such as the Glyme. Crayfishes were as abundant 

 in Continental rivers, but they too suffered from a pest 

 which greatly thinned their numbers in 1876, and they are 

 so persistently fished for, that they are no longer as common 



Digitized by Microsoft® 



