14 DEEP SEA FISHES. 
the Fardée Channel at depths of 300 to 465 fathoms, in temperatures of 
31° to 33°, and at the surface, the temperature of which was 54° F. In the 
northwestern Atlantic this 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 2369 fathoms where the heat 
was less than 36° F. From the foregoing data this fish has a thermal range 
of 42.3° F. and a bathymetrical range of 2569 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 surface, 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 passage 
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 thinner, 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 made by 
the weight of the water, the softness in specimens brought to the surface 
resulting from decrease in the amount of pressure. 
A noticeable change in fishes that attends their departure 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. The change to the 
darker coloration is illustrated by several species of the Halieutoids figured 
below. Malthopsis sparsa of Plate XVUL., from depths of 200 to 822 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- 
