#Om niv' o rous#, eating or living upon food of all kinds. #O per' cu lum#, a lid or cover. #O' ral#, pertaining to the mouth. #Oral groove#, a funnel-shaped groove in one side of some one-celled animals conducting food to the mouth. #Or' der#, a term in classification used to designate a group of genera. #Or thop' ter a#, the order to which locusts, grasshoppers, etc., belong. #Os' cu lum# (pl. #oscula#), the large opening from the central cavity in sponges. #Os mo' sis#, the process by which fluids of different densities become equally diffused when separated by an organic membrane or by a porous structure. #Os' ti a# (sing. #ostium#), the inner ends of the canals in the body-walls of sponges. #O' va ry#, the organ in which the egg cells are developed. #O vi pos' i tors#, organs used to deposit eggs. #Pal' li al#, a line connecting the two muscle scars in a bivalve shell. #Palp#, (1) a jointed finger-like structure on the oral appendages of arthropods; (2) oral appendages found in mollusca. #Pan' cre as#, one of the glands of the digestive system. #Par a nu' cle us#, _see_ Nucleolus. #Par' a si tism#, an association of two animals, one living at the expense of the other. #Pec' to ral#, (1) pertaining to the thorax or breast; (2) the anterior of the paired fins of fishes. #Pelvic#, (1) pertaining to the pelvis; (2) the posterior paired fins of fishes. #Pen#, a remnant of exoskeleton found in the squid. #Per i car' di um#, a membranous bag surrounding the heart. #Per is so dac' tyl#, ungulates with an odd number of toes. #Per' i to ne' um#, a membrane that lines the body cavity. #Pha' lanx# (pl. #phalanges#), one of the bones of the fingers or toes. #Phar' ynx#, the region of the alimentary canal just back of the mouth cavity. #Pigment#, a substance which gives color to an object. #Plan' ti grade#, walking on the soles of the feet; flat-footed. #Pol' len bas ket#, the flattened hairy tibia of the hind legs of honey bees, used for carrying pollen. #Pol' lin na tion#, the transfer of pollen from the anther of a flower to the stigma. #Polyp#, any radially symmetrical animal, but usually an individual in a connected colony. #Po rif' e ra#, the sponges, distinguished by the canals which perforate the body wall. #Post em bry on' ic#, development after birth or hatching. #Pos te' ri or#, situated behind or toward the hinder part. #Pro bos' cis#, a prolonged, flexible snout or a tubular structure, protruding from the head. #Pro' leg#, an unsegmented appendage found in the larvæ of some insects. #Protective resemblance#, a method of protection due to the resemblance of an animal to its background. #Pro tho' rax#, the most anterior division of the thorax. #Pro' to plasm#, the living material composing the cell; the physical basis of life. #Pro to zo' a# (sing. #protozoön#), animals of one cell, existing alone or in loose colonies. #Prox' i mal end#, the attached end of anything which has also a free end.