Page:Popular Science Monthly Volume 61.djvu/202

196 Sacramento pike and split-tail. Some of them, at least, are caught in the eddies formed among the cobble stones, and are held near the 'nest,' or hillock of gravel thrown up by the spawning fishes. These

are covered by the sand and protected, though many are covered too deeply and are killed.

Salmon ova are about .25 inch in diameter. The 'shell' is membranous and finely porous, with a minute aperture, somewhat larger than the pores, known as the micropyle. When first extruded the ova

are soft and compressible, and it is while in this condition that they must be fertilized. Within two or three minutes after being deposited in the water they become turgid, and are then incapable of fertilization.