Page:The New International Encyclopædia 1st ed. v. 06.djvu/783

* EGG. 679 KGG. bugs, assume grateful, flask-like shapes and ele- ^'antly sculptured surtai-es. Otlier insects — the goldeu-eye tlics, for oNaniple — -pmduee stalked eggs, which are raised well above the ])laiit-stem on which they are laid, and so protected from mites and other eiieniics. Insect-egus contain a quantity of food-yolk, and are therefore of eom- jiaratively large size. The globular egg of the iiawkiMotli. for instance, measures .,y inch in diameter, while the similarly slia|)ed egg of a cat measures only [Jj inch. The cockroach's eggs are protecteil by a purse-shaped capsule. Sixteen eggs are contained in this case, eight on a side. . . . Many insects protect their eggs by a gummy secretion; some female moths shed hairs from their bodies to afTord the eggs a covering. Those of the water-insects are often contained in a long gelatinous tube, and some water-beetles con- struct around their eggs a silken cocoon. Lo- custs, grasshoppers, and many other insects bury their eggs in the ground for safety: other insects — chafers and crane-Hies, for example — lay their eggs in the ground that the young may be near the roots of plants on which they will feed. Almost universally the food of the young determines the place of egg-laying." The eggs of » certain small aquatic fly, breed- ing in Western saline lakes, drift on shore in vast quantities, and are baked into edible cakes by the local Indians. Eggs of Crustace.. Some crustaceans pro- duce masses of agglutinated eggs, which the female carries about with her. attached to her abdominal appendages, until they hatch. Others lay comparatively few eggs, which are carried about by the female in one or two special sacs: while many simply set their numerous small eggs free in the water. 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 arc 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 ( Pelecypoda ) pour out immense quantities of minute eggs and sper- matozoa into the water, to meet if they can. A large proportion of this will be 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 afTorded by the fresh-wafer mussels. whi<h kee|) their eggs within their sludls, inclosed within the gills and mantle, and so protect them. Among gastropods the eggs arc comi)aratively few and well eared for. "In almost all the C!astropoda." say Parker and Haswidl. "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 egL's imbedded in it. at- tains a relatively considerable size. In form it varies greatly: very often it is in the shape of lnn2 strings, which are cylindrical or band-like; sometimes several such strings arc twisted to- gether into a cord. Sometimes the spawn is fixed to seaweed or oilier objects; sometimes it is unat- tached and may float about freely. In the Ktrep- toncura, 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 similar object. ... In the land Pulmonata (snails) each ovum 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 arc im- bedded in a rounded gelatinous mass. Isually. as in Helix 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." The A>'NELIDS (Annulata) give comparatively large ova, and each has a double gelatinous envelope and contains food-yolk: some cast them abroad; by many they are inclosed in packets or cocoons (as is the case in the earthworm), or stick together or to the parent or to some out- side object. The egg of the flatworms has a pro- tective chitinoid integument, contains food-yolk, and sometimes ( as among mollusks, insects, etc. ) has an opercuhun facilitating the escape of the matured embrvo; also external cement for at- tachment to each other or to some fixed object. The same is true of nematodes, which oviposit vast numbers of eggs — 1.5.000 a day, it is stated. The Trochelminthes (rotifers) lay eggs of three kinds, those produced in the autumn having thick shells to enable them to survive the winter and develop in the spring. Polyzoans and brachiopods ]iroduce very few eggs at a time, and these are developed into larvje in 'brood-pouches' within the body. The eggs of echinoderms are minute globules, consisting of germ-cell, food-yolk, and a glassy exterior layer. They are generally set free in the water, where they are fertilized and devel- oped. Sometimes they stick to the surface upon which they are laid, and develop there. The eggs of coelenterates and sponges are hardly worthy of the name, being merely micros<'opic germ-cells, set free in vast quantities as one of several means of reproduction. Bibliography. .Standard 'Matural Eistory (6 vols., Boston. 188.5) ; Parker and Haswell. Trxt- Bonk of Zoolofii/ (London and New York, 1897) ; Flower and Lydckker, Mnmiunls, Liriny and Ex- tinct (London. ISOl): Xewton, article "Eggs," with manv bibliographical references, in Dii-tiim- anj of 'liinix (London. lS!)3-n6) ; Wallace. nannnism (London, 1880); Poulton. Colors of Aiii)nals (London and Xew York, 1800) ; Inger- soll, "A Bird's Egg," in Harper's Magazine (New Y'ork, December, 1897) ; Gunther, Study of Fishes (London, 1880) ; Publications I'nited States Fish Commission (Washington, 187.5 to the present) ; Kirby and Spence. Introduction to Kntomolofiy (London. 1828) ; C'arpenfer, /nsrrts: Their Strueture and Life (London, 1800) ; Pack- ard. A Text-book of Entomoloiiy (Xew York, 1808). EGG. In plants, the more technical term for the egg is 'oii»j)hcre.' Among the lowest jilants in which sexuality is developed, such as the