848 Appendix 



Paedogenesis (pedogenesis) (pe do -jen' e sis) (Gr. pais, child; genesis, origin), 

 reproduction by a larval or embryonic stage rather than by an adult. 



Paleobotany (pa le o -bot' a ni) (Gr. palaios, old; botane, plants), science of 

 ancient plants. 



Paleontology (pa le on -tol' o ji) (Gr. palaios, old; logos, study), science of plant 

 and animal life of the past geologic periods. 



Paleozoology (pa le o zo ol' o ji) (Gr. palaios, old; zoa, animals; logos, study), 

 study of ancient animals. 



Palisade layer (pal' i sade) (L. palus, stake), columnar cells with chloroplasts 

 in the mesophyll tissues of leaves, just below the upper epidermis. 



Pancreas (pan' kre as) (Gr. pan, all; kreas, flesh), an accessory digestive gland. 



Pangenesis (pan -jen' e sis) (Gr. pan, all; genesis, origin), Darwin's theory that 

 all body cells give rise to minute particles called pangenes which migrate 

 to the germ cells and impress their traits upon them (theory not accepted 

 today). 



Parallelism {see Convergent adaptations or Variations). 



Paramecin, a "killer" particle in a Paramecium. 



Paramylum (par -am' i lum) (Gr. para, beside; amylon, starch), starchhke sub- 

 stance in certain protozoa. 



Paraphyses (pa -raf i sez) (Gr. para, beside; physis, growth), sterile, hairlike 

 structures associated with sex structures in certain algae, fungi, mosses, etc. 



Parapodium (par a -po' di um) (Gr. para, beside; pons, foot), paired processes on 

 the body segments of the sandworm (nereis) of the phylum annelida. 



Parasite (par' a site) (Gr. para, beside; sitos, food), a plant or animal living in 

 or on another living organism ; livdng at its expense. 



Parathyroid (par a -thi' roid) (Gr. para, beside), four small endocrine glands ad- 

 jacent to the thyroid. 



Parenchyma (pa -reng' ki ma) (Gr. para, beside; en, in; chein, to pour), spongy 

 mesodermal tissues of lower animals or fundamental plant tissues as op- 

 posed to more highly differentiated plant tissues. 



Parotid (pa -rot' id) (Gr. para, beside; otos, ear), salivary gland located below 

 the ear. 



Parthenogenesis (par the no -jen' e sis) (Gr. parthenos, virgin; genesis, origin), 

 development of an egg without fertilization by a male sperm. 



Pasteurization (pas ter i -za' shun) (after Pasteur), killing certain organisms by 

 heating a liquid to 142°-145° F. for thirty minutes (212° F. is boiling). 



Patella (pa-tel'a) (L. patena, pan), kneecap. 



Pathogenic (path o -jen' ik) (Gr. pathos, suffering; genesis, origin), disease-pro- 

 ducing. 



Pathology (pa thol' o ji) (Gr. pathos, suffering or disease; logos, science), study 

 of diseased or abnormal conditions. 



Pecten (pek' ten) (L. pecten, comb), comblike structure in certain insects. 



Pectoral (pek' to ral) (L. pectus, breast), pertaining to chest or breast. 



Pedal (ped' al) (L. pes, foot), pertaining to the foot. 



Pedicelaria (ped i se -la' ri a) (L. pediculus, small foot), small, pincerlike struc- 

 tures on the surface of certain echinoderms such as the starfish. 



