GLOSSARY 917 



Pelagic (pelaj'ik), floating near the surface of water. 

 Pericardial (per I kar'di al), situated around the heart. 

 Periosteum (per i os'te um), the membranous covering of bone. 

 Peripheral nervous system (pe rif'er al), that part of the nervous system ex- 

 clusive of the brain and spinal cord. 

 Peristaltic (per i stal'tik), forcing the food along the intestine by rhythmical 



contractions of the intestinal wall. 

 Peritoneum (peri tone'um), the membrane that lines the coelom of vertebrates. 

 Petromyzontia (pet ro mi zon'ti a), subclass of Cyclostomes including the lamp- 

 reys. Tlie name means stone and suck. 

 Phagocyte (fag'6 sit), a white corpuscle which engulfs and destroys bacteria 



and other foreign material. 

 Pharynx (far'ingks), the region between the mouth and the esophagus. 

 Pharyngeal (fa rin'je al), pertaining to the pharynx. 

 Phenotype (fe'notip), a tj-pe of organism possessing a complex of characters 



in its external features. 

 Phenotypic (fe n6 tip'ik), pertaining to phenot\T3e. 



Photosynthesis (fo to sin'the sis), the process by which green plants manufac- 

 ture starch from raw materials. 

 Phototropism (fo tot'rfi piz'm), response of an organism to light. 

 Phylogeny (fi loj'eni), the study of the origin and relationships of the different 



groups and races of organisms. 

 Physiology (fiziol'o ji), the study of the function of the parts of an organism 



as well as its living processes as a whole. 

 Pia mater (pi'ama'ter), the membrane which is the immediate covering of 



the brain and spinal cord. 

 Piliditmi (pT lid'ium), helmet-shaped larva of certain forms. 

 Pineal (pin'e al) body, a dorsal projection from the diencephalon and thought 



to be the vestige of a third or median eye in vertebrates. 

 Pituitary (pitu'iteri) body, a glandular structure attached to the neutral 

 side of the diencephalon of the vertebrate brain. It is an endocrine 

 organ. 

 Placenta (plasen'ta), the vascular membrane which connects the embryo with 



the parent. 

 Placula (plak'ula), a t\-pe of blastula in which the animal and vegetative 



halves are somewhat compressed toward each other. 

 Plankton (plangk'ton), the small pelagic organisms which are at the mercy of 



the waves. 

 Plasma (plaz'ma), the fluid portion of the blood. 



Plasmagel (plaz'ma jel), the viscous or semisolid portion of protoplasm. 

 Plasmasol (plaz'ma sol), the more fluid phase of protoplasm. 

 Plasmosome (plaz'mo som). (See Nucleolus.) 



Pleural (pldbr'al), pertaining to the cavity which contains the lungs. 

 Plexus (plek'sus), a network. 

 Polar (po'ler) body, a small nonfunctional cell or oocyte produced during the 



maturation divisions of the female germ cell. 

 Polarity (p61ar'iti), referring to a condition in which points or poles of con- 

 centration or dominance are established in a body. 

 Polocyte (po'16 sit), a technical name for a polar body. 



Polyandry (pol'I an dri), the practice of one female mating with several males. 

 Polygamy (pSlig'ami), having more than one mate at the same time. 

 Polygyny (p6 1ij'ini), the practice of one male mating with several females. 

 Polymorphism (poli mor'fiz'm), the occurrence of two or more forms of in- 

 dividuals within a species. 

 Polyp (pol'ip), the attached phase of the life history of a coelenterate animal. 

 Precocial (pre ko'shal), tjT)e of bird which leaves the nest and has downy cover- 

 ing at time of hatching. 



