#Dor' sal surface#, the upper surface; the back. #Du' o de' num#, the first portion of the small intestine. #Ec' to derm cells#, cells covering the outside of sponges and some other simple animals. #Egg cell#, the large, non-motile reproductive cell, with which a sperm cell fuses. #Em bry on' ic#, development within the egg or in the body of the mother. #En' do derm cells#, cells lining inner cavities in the many-celled animals. As a rule they have cilia or flagella. #E soph' a gus#, the portion of the alimentary canal connecting the mouth (or the pharynx) with the stomach. #Eu sta' chi an# (eu sta' kian) #tube#, a passage between the pharynx and the middle ear. #Ex ha' lent#, flowing or moving away from the body. #Ex' o skel' e ton#, an external skeleton. #Eye stalk#, an appendage which bears an eye on its free end. #Fe' mur#, (1) the thigh bone; (2) the third joint of an insect's leg. #Fer ti li za' tion#, the fusion of male and female elements in reproduction. #Fi' bers#, flexible threads; fibers of a horny material are found in the walls of many of the sponges. #Fib' u la#, the outer of the two long bones of the lower leg. #Fin#, a paddle-like structure for swimming. #Fin-rays#, the framework of the fins of fishes. #Fis' sion#, a method of reproduction used in all cells, by which a cell divides itself into two, usually through the center. _See also_ Conjugation and Budding. #Fla gel' lum# (pl. #flagella#), vibrating hairs larger than cilia and less numerous. #Food-balls#, bits of food inside the cells of many one-celled animals, usually showing through the walls. #Food-vacuole#, a small drop of water containing digestive material and a food-ball. #Fo ra' men#, an opening or short passage. #Gall-bladder#, a membranous sac for the storage of gall, or bile, at the lower edge of the liver (syn. "bile sac"). #Gas ter op' o da#, the class to which the snail belongs. #Ge' nus# (pl. #genera#), a group of closely related species. #Germ-spot#, the region in the bird's egg in which development first takes place. #Gill#, an apparatus for breathing the air dissolved in water. #Gill-cham' ber#, a pocket or cavity covered by a flap, in which the gills lie. #Gir' dle#, the name applied to the smooth band often occurring near the anterior end of an earthworm. #Giz' zard#, a portion of the alimentary canal with especially thickened muscular walls. #Glot' tis#, the opening between the vocal cords, or the mouth of the windpipe. #Gre ga' ri ous#, associations of animals with little division of labor; gathering in flocks, herds, etc. #Gullet#, the inner end of the oral groove. #He mip' te ra#, insects with a piercing organ for sucking their food, Bugs. #He pat' ic#, pertaining to the liver. #Her biv' o rous#, plant-eating. #Hock#, the joint of the hind leg situated between the tibia and tarsus, corresponding to the ankle in man. #Hu' me rus#, the long bone of the upper part of the arm or fore limb.