340 



THE BIOLOGY OF MARINE ANIMALS 



above the surface succeeds in entering the water. The velocity of sound in 

 water is given by the formula 



where y is the ratio of specific heats, q is the density of the liquid, and K 



Fig. 8.25. Responses of Muscle Receptor Organs of the 

 Crayfish {Procambarus allen'i) to Stretch 



Above (A,B) slow cell. A, cell impaled and stretched just above threshold, setting up five 

 irregular discharges. At second arrow, increased stretch raised discharge rate. B, cell 

 subjected to gradually increasing stretch between first arrow and straight line, and then 

 held constant. The discharge is regular during maintained stretch. Gap of several 

 seconds in record. Below(A,B,C) adaptation of impaled fast cell during maintained stretch. 

 A, slow stretch for 2 sec at first arrow, additional stretch at second arrow maintained for 

 4-5 sec. Gap at B, when additional maintained stretch applied (third arrow). C, fast 

 cell, extracellular recording. Steady stretch applied between arrows 1 and 2; further 

 stretch added at arrow 2 and maintained until arrow 3. Time, lsec. (From Eyzaguirre 

 and Kuffler (45).) 



the compressibility. The three variables y, g and K change with tempera- 

 ture, salinity and pressure. When these are known the velocity can be 

 determined from suitable tables (106). The intensity of sound in water 

 varies inversely as the square of the distance from the source. Absorption 

 of sound energy becomes significant only at high frequencies (138). 



