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Page:Popular Science Monthly Volume 56.djvu/498

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484
POPULAR SCIENCE MONTHLY.

at rest. If the needle is placed behind the fish, it will swim directly forward; if at the side or about the middle, it causes the fish to swim directly forward or to turn and swim in a direction opposite the origin of the disturbance. Younger specimens have, as yet, no power over the direction of their progress; the wiggling of the tail simply produces a gyration, with the yolk as pivot.

A young blind fish, six months old, swims about in a jerky manner, chiefly by the use of its pectoral fins. It keeps close to the side of the vessel, usually with its back to the glass. (The aquarium was a cylindrical jar three hundred millimetres in diameter and three hundred millimetres high.) It perceives a stick thrust toward it as readily as a seeing fish can. It always perceives from whatever direction it may be approached, and will invariably dart away a short distance, sometimes making sharp turns to avoid the stick, and always successfully. It can be approached from the top nearer than from the sides or from in front. It does not avoid the sides of the aquarium, which it frequently strikes. It is a bottom feeder; its intestinal canal is always partially full.

A long series of experiments was made on Amblyopsis and Chologaster to determine their reaction to white and monochromatic light. Without going into the details of these experiments, it may be stated that Amblyopsis avoids the light, regardless of the direction or the color of the rays. The same is true of Chologaster, except that they were positively attracted by the red rays of the spectrum as against the blue.

We owe the first observations on the breeding habits of Amblyopsis to Thompson, who states that a fish "was put in water as soon as captured, where it gave birth to nearly twenty young, which swam about for some time, but soon died; … they were each four lines in length." Little or nothing has been added to our knowledge of this subject since that time, but the highly interesting supposition of Thompson that they were viviparous has gained currency, and it is therefore unfortunate that in this respect he was in error.

Putnam adds to the above that, judging from some data in his possession, the young are born in September and October, and further along remarks that they are "undoubtedly" viviparous.

The eggs are laid by the female in under her gill membrane. Here they remain for perhaps two months, till the yolk is nearly all absorbed. If a female with young in her gill pouches is handled, some of the young are sure to escape. This was observed, and gave rise to the idea that this fish is viviparous. Eggs have been obtained as early as March 11th and as late as September, and the indications are that the breeding season extends throughout the