14 DEEP SEA FISHES. 



tlie Faroe Channel at depths of 300 to 4G5 fathoms, in temperatures of 

 Sr to 33", and at the surface, the temperature of which was 54° F. In the 

 northwestern Atlantic tliis Scopeloid is said to have been taken by the 

 '' Blake," the " Fish Hawk," and the " Albatross " on the surface where 

 the temperature was 72°, and at a depth of 23G9 fathoms where the heat 

 was less than 3G' F. From the foregoing data this fish has a thermal range 

 of 42.3" F. and a bathymetricnl range of 2369 fathoms. This would indicate 

 that the thermal limits to distribution are hardly more confining than those 

 set by pressure ; yet there is abundant evidence that particular species 

 affect rather narrow thermal limits and are rarely found much beyond 

 them. Comparatively the number of the species that leave the lower belt 

 of light and approach the surHice, crossing the " azoic zone," is probably 

 small. If the fishes are able to sustain themselves in a temperature of 

 freezing or lower there evidently is no barrier but distance to the jiassage 

 of a migratory species through the Arctic Ocean from the Atlantic or 

 the Pacific. 



There appears to be a general modification attendant on the progress 

 of the fishes from the shoals to the abysses in which the tissues become less 

 firm, the bones more cartilaginous, the scales tliinner, and the entire body 

 in cases becomes almost gelatinous ; but when in the depths the bodies are 

 not supposed to be at all soft and flabby, compensation for the lack of firm- 

 ness, from reduction in the amount of lime or other causes, being nuide by 

 the Aveight of the water, tlie softness in specimens brouglit to tlie surface 

 resulting from decrease in the amount of pressure. 



A noticeable change in fishes that attends their dejaarture from the sun- 

 light on the way to the great depths is that of coloration : the spots, bands 

 and other special markings common near the surface disappear and the 

 appearance becomes uniform, most often of a dark brown to black, with, on 

 those not habitually dwelling in the mud or the dark belt, an added assimi- 

 lative or occultative tint to bring the surfaces into harmony with the pale 

 greenish to yellowish green light of the ocean bottom. Tlie change to the 

 darker coloration is illustrated by several species of the Halieutoids figured 

 below. Malthopsis sjxirsa of Plate XVIII., from depths of 200 to 322 fathoms 

 has a coloration that fixes the species as an inhabitant of zones within the 

 reach of sunlight at recent dates, possibly a portion of each year ; gen- 

 erally it is grayish brown with yellowish to white reticulations surround- 



