GLOSSARY 



697 



Pe-lag'ic (L. pelagicus, from pelagus, sea). 

 Inhabiting the open sea. 



Perii-cle (L. pellicula, small skin). A thin 

 skin, or film. 



Pe'nis (L.). The male organ of copnlation. 



Pen'ta-dac"tyl (Gr. pente, five; daktylos, 

 finger). Having five digits. 



Pep'sin (Gr. pepsis, a cooking, digesting). 

 The protein-splitting enzyme of the 

 gastric juice. 



Per'i-car"di-um (Gr. peri, around; cardia, 

 heart). The membranous sac surround- 

 ing the heart. 



Per'i-os"te-um (Gr. peri, around; osteon, 

 bone). The tough, fibrous membrane 

 surrounding bone. 



Pe-riph'er-al (Gr. periphereia, from peri, 

 around; pherein, to bear, carry). Per- 

 taining to the surface. 



Per'i-star'sis (Gr. peri, around; sfalsis, con- 

 striction). The wave of contraction by 

 which the alimentary canal propels its 

 contents. 



Per'i-to-ne"um ( Gr. peri, around; tenein, to 

 stretch ) . The thin epithelial membrane 

 which lines the coelom and invests the 

 viscera. 



Phag'o-cyte (Gr. phagein, to eat; kijtos, 

 cell ) . A type of white blood cell which 

 ingests foreign substances. 



Pha-lan'ges ( Gr. phalanx, long line of bat- 

 tle). Digital bones. 



Phar'ynx (Gr. pharynx). The portion of 

 the digestive tract located between the 

 mouth and esophagus. 



Phe'no-type (Gr. phaino, show; tijpto, 

 strike). The total of visible and phys- 

 iological traits common to a group of 

 individuals. 



Pho'to-syn"the-sis (Gr. phos, light; synthe- 

 sis, a putting together). The chemical 

 combination, in the green plant, of car- 

 bon dioxide and water, to form carbo- 

 hydrate, in the presence of light and 

 chlorophyll. 

 Phy-log'e-ny (Gr. phylon, race, branch; 

 geny, become). The evolutionary his- 

 tory of a race or group. 



Phy'lum (Gr. phylon, tribe). One of the 

 main divisions of the animal or plant 

 kingdom. 



Phys'i-ol"o-gy (Gr. physis, nature; logos, 

 study). The study of functions of or- 



ganisms. 



Pig'ment (L. pingere, to paint). Coloring 



matter. 

 Pin'e-al (L. pinea, pine cone). An evagi- 

 nated structure on the roof of the 

 brain. 



Pi-tu"i-tar'y bod'y (L. pituita, phlegm; A.S. 

 bodig). An endocrine gland. 



Pla-cen'ta (L. placenta, a flat cake). The 

 round, flat organ within the uterus of 

 mammals formed during embryonic de- 

 velopment and attached to the embryo 

 by means of an umbilical cord. 



Plan'u-la (L. planus, flat). The ciliated, 

 free-swimming larva found in the de- 

 velopment of certain invertebrates. 



Plas'ma (Gr. something molded). The liq- 

 uid part of the blood or lymph. 



Plas'ma mem'brane (L. membrana, skin 

 covering). The external cytoplasmic 

 membrane of a cell. 



Plas'tid (Gr. plastides, to form). A pig- 

 mented cytoplasmic inclusion. 



Plat'y-hel-min''thes (Gr. platy, flat; hel- 

 mins, worm). A phylum of animals. 



Pleur'al (Gr. pleura, side). Pertaining to 

 the cavity in which the lungs are con- 

 tained. 



Plex'us (L. interwoven). A nervous or 

 vascular network. 



Po'lar bod'y (L. polaris, axis). Tlie non- 

 functional cell formed during the mat- 

 uration of the egg cell. 



Pory-mor"phism (Gr. polys, many; morphe, 

 form). The occurrence of more than 

 two types of individuals in the same 

 species. 



Pol'yp (Gr. polypous, many-footed). The 

 attached form of a coelenterate usually 

 possessing a mouth and tentacles at 

 the free end. 



Pos-te'ri-or (L. latter). Situated behind. 



Pre-co'cious (L. praecox, ripe before its 



