No. 545] THE BIOLOGY OF THE CRAYFISH 



2*3 



Hearing.— It lias been pretty clearly demonstrated by 

 Bell that the crayfish has no sound reactions. He tried 

 experiments (16) such as rapping on a board floating in 

 the water, snapping a metal snapper in and out of the 

 water, and setting tuning forks in vibration in the water, 

 but got no response. 



It is possible that the crayfish is sensitive to the sound 

 made by the movement of the inn nth parts of another 

 crayfish. This has not been proved. 



En ii'h lib riu in. — Bunting found that young crayfish with 

 the statocysts removed would swim upside down as 

 readily as right side up (18). It is also pretty certain 

 that the older crayfish have a sense of equilibrium, 

 although the response to rotation in their case is not 

 definite, but purely individual. 



Mating, Spawning and Development. 

 The process of mating in Astacus differs from the 

 process in Cambarus. In the case of Astacus, the males 

 approach the females in October, November and January. 



and deposits the spermatic manor. tiiJl.v mi the external plates of the 

 caudal fin, secondly on the thoracic sterna anmml the external open- 



The female of Cambarus differs from the female of 

 Astacus in having a false pouch, the annulus ventralis. 

 Andrews found that this pouch does not appear in Cam- 



