Page:Popular Science Monthly Volume 56.djvu/499

Rh year. The eggs are large—2.3 millimetres in diameter from membrane to membrane—and about sixty to seventy are laid at one time.

Certain structures gain an entirely new significance in the light of the breeding habits. These are the enlarged gill cavities, with the small gills, the closely applied branchiostegal membrane, and the position of the anus and sexual orifices. The latter are placed just behind the gill membrane in such close proximity to it that they can be covered by it. It is probable, therefore, that the membrane is drawn over the sexual orifice and the eggs deposited directly into the gill cavity. In an individual thirty-five millimetres



long the anus is situated between the origin of the pectorals; in one twenty-five millimetres long it lies between the pectorals and ventrals. In the young it lies behind the ventrals, as in other fishes.

In an aquarium containing six Amblyopsis two took a great antipathy to each other. Whenever they touched, a vigorous contest began. Frequently they came to have a position with broadside to broadside, their heads pointing in opposite directions. At such a time the fight consists in quick lateral thrusts toward the antagonist to seize him with the mouth. The motion is instantly parried by a similar move by the antagonist. This blind punching may be kept up for a few seconds, when, by their vigorous motions, they lose each other and jerk themselves through