GLOSSARY 



683 



ventral surface of the brain and composed 

 of anterior, posterior, and intermediate lobes. 



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

 for attaching the fetus of mammals to the 

 uterine wall; it serves in fetal nourishment, 

 respiration, and excretion. 



Plan'ti-grade (L. planta, sole; gradi, to step). 

 Walking with the whole sole of the foot; 

 bearing on the ground as does the bear or 

 man. 



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

 swimming, larval form of most coelenterates. 



Plas'ma (Gr., something molded). The liquid 

 part of the blood or lymph. 



Plas'ma mem'brane (Gr., something molded, 

 L. membrana, skin covering). The external 

 membrane formed bv the cytoplasm of a 

 cell. 



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

 body found in certain cells, often containing 

 pigment. 



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

 worm ) . Phylum which includes the flat- 

 worms such as the planaria. 



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

 cavity, that portion of the coelom, which 

 contains the lungs. The membrane covering 

 the lung and lining the pleural cavity. 



Pleur'on (Gr., side). The lateral portion of a 

 typical segment of such an arthropod as the 

 cravfish. 



Plex'us (L., interwoven). A network, chiefly of 

 nerves or blood vessels. 



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

 functional cell thrown off during the meiosis 

 (maturation) of the egg cell. 



Pol'y-mor'phism (Gr. polys, many; morphe, 

 form). The occurrence of more than one 

 form in a single species; when only two such 

 forms occur, dimorphism is the term usually 

 applied, hence polymorphism, according to 

 usage, implies more than two such different 

 forms. 



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

 of a coelenterate having the shape of an 

 elongated cylinder fastened at the aboral 

 end, with mouth and tentacles at the free 

 oral end. 



Pos-te'ri-or (L., latter). The tail, or toward the 

 hind or rear end. Opposite of anterior. 



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

 Characterized by early maturity. 



Pre-da'ceous (L. praedo, prey). Capturing liv- 

 ing animals for food. 



Pre-niax-il'lae (L. prae, before; maxilla, jaw). 

 A pair of anterior bones of the upper jaw in 

 \ertcbratcs. 



Pri-mor'di-al (L. primordiwn, beginning). 

 First in order of time; the primitive form. 



Prin'ci-ple (L. principium, beginning) . A scien- 

 tific theory, fact, or law of wide applica- 

 tion. 



Pro-bos'cis (Gr. proboskis, trunk). A tubular 

 extension of the nose, lips, or pharynx. The 

 extended bcaklike mouth parts of insects. 



Pro-neph'ros (Gr. pro, before; nephros, kid- 

 ney). The first kidney embryologically 

 formed in the vertebrate. 



Pro-nu'cle-us (Gr. pro, before; L. nucleus, 

 kernel). One of the two nuclear bodies of a 

 fertilized egg, the male pronucleus and the 

 female pronucleus, the fusion of which re- 

 sults in the cleavage nucleus. 



Pro'phase (Gr. pro, before; phasis, appear- 

 ance). Any one of the first stages of mitosis 

 during which the chromosomes become dis- 

 tinctly visible. 



Pros'o-pyle (Gr. proso, forward; pyle, opening) . 

 One of the surface pores opening into a 

 chamber of a sponge. 



Pros'tate gland (Gr. prostates, one who stands 

 before; L. glans, acorn ) . A gland surrounding 

 the neck of the bladder and urethra in the 

 male mammal. 



Pro-sto'mi-um (Gr. pro, before; stoma, 

 mouth ) . The anterior portion of the first 

 segment of the annelids such as the earth- 

 worm, overhanging the mouth region. 



Pro'te-in (Gr. protos, first). An organic com- 

 pound always containing nitrogen, carbon, 

 oxvgen, and hvdrogen, and often other ele- 

 ments. Each is made up of amino acids and 

 is an essential part of protoplasm. 



Pro'to-plasm (Gr. protos, first; plasma, some- 

 thing molded). The living substance of 

 which all organisms are composed; it is a 

 complex ph^sicochcmical colloidal solution 

 and constitutes the physical basis of life. 



Pro-top'o-dite (Gr. protos, first; pous, foot). 

 The basal portion, usually composed of two 

 segments of a biramous appendage, of a 

 crustacean, such as the crayfish. 



Pro'to-zo"a (Gr. protos, first; zoion, animal). 

 The phylum of animals, usually unicellular. 



