GLOSSARY 395 



Parietal bone (pa ri' e tal). One of a pair of bones on the posterior upper part of the 



skull of vertebrate animals. 

 Parrakeet {par' ra heet). One of a number of small parrots. 



Parthenogenesis {par' the no jen' e sis). The development of an egg without fertiliza- 

 tion. 

 Parthenogonidia {par' the no go nid' i a). The asexually reproducing cells of Volvox. 

 Pasteur, Louis (pas ter'). French chemist and bacteriologist, 1822-1895. 

 Paternal {pa ter' nal). Pertaining to or derived from the father. 

 Pecten {pek' ten). A genus of bivalve mollusks. 

 Pectoral girdle {pek' to ral ger' d'l). A group of connected bones serving to attach 



the bones of the fore hmbs of vertebrate animals to the rest of the skeleton. 

 Pelagic {pe laj' ik). Pertaining to the open water of a lake or ocean, not near the 



shore nor far below the surface. 

 Pelecypoda (pel' e sip' o da). A class of Mollusca having bivalve shells and a bilobed 



mantle; the clams and mussels. 

 Pellicle {pel' li k'l). A thin skin or film on the surface of a cell. 

 Pelomedusidae {pel' o me du' si dee). A family of turtles. 

 Pelvic girdle {pel' vik ger' d'l). A group of bones serving to join the bones of the hind 



limbs of vertebrate animals to the rest of the skeleton. 

 Penis {pe' nis). The copulatory organ in the male of many animals. 

 Pentadactyl {pen' ta dak' til). Having five fingers or toes. 

 Pentamerous {pen tarn' er us). Five-parted, or arranged in groups of five. 

 Pepsin {pep' sin). An enzyme of the stomach of vertebrate animals, whose function 



is digestion of many kinds of proteins. 

 Pepsinogen {psp sin' ojen). An inactive substance from which the enzyme pepsin is 



derived. 

 Peptic {pep' tik) . Of the nature of pepsin ; said of proteolytic enzymes that act in an 



acid medium. 

 Peptone {pep' tone). Any of a number of substances, derived by hydrolysis from 



proteins, which are not precipitated by ammonium sulphate. 

 Peranema {per' a ne' ma). A genus of colorless flagellate Protozoa. 

 Pericardium {per' i kar' di um). The membranous sac enclosing the heart. 

 Periodic {pe' ri od' ik). Occurring at rather regular intervals; said of migration which 



depends on the seasons or on the age of the migrating animals. 

 Peripatus {perip' a tus). A genus of arthropods with elongated wormlike bodies, 



belonging to the class Onychophora. 

 Perisarc (per'isark). The tough sheath surrounding the stalk and branches of a 



hydroid. 

 Peristalsis {per' i staV sis). The rhythmical contraction of the walls of the intestine. 

 Peritoneum {per' i to ne' um). A sheet of cells covering the viscera and lining the 



body cavity in many animals. 

 Perivisceral {per ' i vis' ser al) . Around the viscera, or organs contained in various 



body cavities. 

 Permeable {per' me ab'l). Permitting the passage of both hquids and dissolved 



substances. 

 Permian {per' mi ari). Belonging to the close of the Carboniferous age. 

 Petrifaction {pet" ri fak' shrin) . The substitution of mineral matter for organic matter 



in the remains of animals or plants. 



