Fig. 4.—Ipnops Murrayi, living at a depth of 1,500 to 2,100 fathoms.
Fig. 5.—Chlorophthalmus gracilis, from 1,100 fathoms, off New Zealand.
I have not found the slightest difficulty in capturing Amblyopsis with a small dip net, either from a boat or while wading through the subterranean stream, and I have caught one in the hollow of my hand. At such a time all the noise I could make did not affect the fishes found swimming in the water. Frequently they were taken in the dip net without apparently noting the vibrations produced in the water until they were lifted out of it; very rarely a fish became evidently scared. Such a one would dart off a few feet or a few inches, and remain on the qui vive. If not pursued, it soon swam off quietly; if pursued, it not infrequently escaped by rapidly darting this way and that; when jumping out of the water, often an abrupt turn in the opposite direction from which it started would land it in the net, showing that their sense of direction was not very acute. At other times, if disturbed by the waves produced by wading, one or another individual would follow a ledge of rock to the bottom of the stream, where it would hide in a crevice. But very frequently, much more frequently than not, no attention was paid either to the commotion produced by the wading or by the boat and dip net. In general, it may be said that the fishes in their natural habitat are oblivious to disturbances of the water until frightened by some very unusual jar or motion, probably a touch with the net, when they become intensely alert. The fact that they are not easily frightened suggests the absence of many enemies, while their frantic behavior if once scared gives evidence either that occasional enemies are present and that they are very dangerous, or that the transmission of the instinct of fear is as tenacious as the transmission of physical characters.
Fig. 6.—Brodula barbata from Havana, Cuba.
Fig. 7.—Stygicola dentatus from the caves of Cuba.
Contrary to Sloan’s observation, that they detect the presence of a solid substance in their path, I have never noticed that those in confinement became aware of the proximity of the walls of the aquarium when swimming toward it. Instead, they constantly use the padded, projecting lower jaw as bumpers. Even an extremely rapid dart through the water seems to be stopped without serious inconvenience by the projecting jaw.
The first observations on the feeding habit of Amblyopsis are those of Cope. He remarks that “the projecting lower jaw and upward direction of the mouth render it easy for the fish to feed at the surface of the water, where it must obtain much of its food.... This structure also probably explains the facts of its being the sole representative of the fishes in subterranean waters. No doubt many other forms were carried into the caverns since the waters first found their way there, but most of them were like those of our present rivers—deep-water or bottom feeders. Such fishes would starve in a cave river, where much of the food is carried to them on the surface of the stream.”
