The Fishes of the Deep Sea 53 



case of invertebrates, often attached to the ground. The 

 ■bassalian fauna grades perfectly into the ordinary shore 

 fauna, yet it has many characteristics of its own. It is 

 largely composed of fishes, yet sea urchins, shrimps, crabs, 

 crinoids and a great number of microscopic forms extend 

 into its region and form part of it. 



In general, the bassalian area lies below the region pene- 

 trated by sunlight. The differences of temperature of day 

 and night, of sumrner and winter, do not extend to it. It is 

 therefore an area of cold and darkness, or uniformity of 

 conditions, and the tremendous pressure of the water keeps 

 the creatures developed in it from extending their range 

 upward or downward. A deep-sea fish rising above its 

 depth is crushed by the reduction of the outside pressure. 

 As the pressure within exceeds that on the outside, its 

 tissues swell, its blood vessels burst, its eyes are forced out, 

 its stomach turned wrong side out. Conversely, a fish sink- 

 ing below the pressure to which it is accustomed is soon 

 crushed or suffocated. Sometimes a deep-sea fish, in a 

 struggle with its prey, is carried above or below its depth, 

 in which case both are destroyed. It will be understood 

 that the tissues of a fish developed below a mile of water 

 are permeated with water of the same degree of pressure 

 as that outside. The deep-sea fish in his normal position 

 no more feels the two thousand three hundred and twelve 

 pounds pressure per square inch of a mile depth of water 

 than we feel the fifteen pounds per square inch of forty 

 miles' depth of atmosphere. 



The greatest depth of the sea yet recorded is approxi- 

 mately six miles. This is found to the eastward of Guam 

 in the mid-Pacific. Being in the mid-Pacific myself, at the 

 time of writing these words, I cannot give the exact figures. 

 At this depth life was found, but no fishes were obtained. 

 The greatest depth at which fishes have been taken is under 

 the Gulf Stream off the Carolina coast, the depth approach- 

 ing five miles, as I remember. 



