A Guide for the Study of Animals Part 62

#O cel' lus#, a simple eye.

#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 cla.s.sification used to designate a group of genera.

#Or thop' ter a#, the order to which locusts, gra.s.shoppers, 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 ca.n.a.ls 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 sh.e.l.l.

#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 a.s.sociation 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 ca.n.a.l 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 ca.n.a.ls 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 larvae 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. #protozoon#), 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.

#Pulsating vacuoles#, _see_ Contracting vacuoles.

#Pu' pa#, the stage in the development of an insect immediately preceding the adult.

#Quill#, one of the large, stiff, strong flight feathers or tail feathers of a bird; the hollow, basal part of a feather; a large, hollow, sharp spine.

#Ra' di al sym' me try#, having the organs or parts arranged symmetrically around a center.

#Re gen er a' tion#, the power to grow new parts or organs.

#Re' gions#, the princ.i.p.al divisions of the body, head, thorax, and abdomen.

#Res pi ra' tion#, the pa.s.sage of oxygen into the tissues of a living organism and of carbon dioxide out of them. These gases can pa.s.s through any thin, moist, organic membrane. When such a membrane separates two fluids which differ in the amount of oxygen they contain, oxygen pa.s.ses to the fluid containing the smaller amount.

The same is true of carbon dioxide. Respiration is believed to occur in all living organisms.

#Ro' dent#, mammals with curved self-sharpening incisor teeth, order including mice, rats, squirrels, rabbits, etc.