EGGS OF THE LOWER INVERTEBRATES. The eggs of the squids and other cephalopod mollusks are enveloped in a tough viscid membrane, and stick together in masses, called 'sea-grapes.' which ad here to some fixed object. They contain much food-yolk. and the young are well advanced be fore leaving the shell. Among the ordinary uni valved and bivalved mollusks a greater variety in respect to eggs is to be met with than might be expected. The bivalves (Peleeypoda ) pour out immense quantities of minute eggs and sper matozoa into the water, to meet if they can. A large proportion of this will he wasted, but a still larger proportion (with the floating eggs of other low marine creatures) serves a very useful pur pose in supplying food to the hosts of fixed crea tures (polyps, sea-anemones, other mollusks., etc.), which can obtain food only as it is brought to them by currents of water. and must trust largely to floating eggs and young. Only a very small percentage is fertilized, and a still smaller part ever matures. An exception is afforded by the fresh-water mussels, which keep their eggs within their sholls, inclosed within the gills and mantle, and so protect them. Among gastropods Slue eggs are eomparativel• few and well eared for. "In almost all the f;astropoda," say Parker and Haswell, "fertilization is internal, and the eggs are laid in great masses imbedded in jelly— each egg having its own hyaline envelope. Very
often the mass of spawn. consisting of the jelly like substance, with the eggs imbedded in it, at tains a relatively eonsiderable size. In form it varies greatly; very often it is in the shape of long strings, which are eylindrieal or hand-like; sometimes several such strings are twisted to gether into a cord. Sometimes the spawn is fixed to seaweed or other objects; sometimes it is mutt taelwd and may float about freely. In the Strep toneura, instead of a jelly-like mass, the eggs are inclosed in a firm parchment-like capsule, in which is contained, in addition to the eggs, a quantity of an albuminous fluid, serving to nour ish the developing embryos. . . Very common ly large numbers of these capsules are aggregated together, and usually they are attached to a rock or a seaweed or sinfilar object. . . . lu the land Pulmonata (snails) each ovuva is sometimes im bedded in gelatinous matter inclosed in a firmer envelope, and a number of them are arranged in a string; sometimes a larger number are im bedded in a rounded gelatinous mass. Usually, as in Ilelix and other genera. the outer layers of the albumen-like substance inclosing the eggs become toughened and impregnated with salts of lime, so as to assume the character of a cal careous shell."