404 THE BIOLOGY OF MARINE ANIMALS 



TABLE 9.4 

 Densities and Sinking Factors for Various Marine Animals 



(Data from Lowndes (72, 73, 75, 78, 79, 80) and Jones and Marshall (61).) 



vagus nerve is believed to contain two categories of nerve fibres : adrener- 

 gic, causing gaseous secretion and contraction of the muscularis mucosa; 

 and cholinergic, causing contraction of the resorbent mucosa. Whether 

 the effect of the secretory nerves is a direct one on the cells of the gas 

 gland, or indirect on the blood supply is unknown. Changes in the tonus 

 of the mucosa appear to be important in determining the direction and 

 magnitude of gaseous exchange (10, 36). 



