522 GLOSSARY 



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



Pleural (pidbr'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 (polar'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 andri), the practice of one female mating with several males. 



Polygamy (p6 lig'ami), having more than one mate at the same time. 



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



Polymorphism (pol i mor'fiz'm), the occurrence of two or more forms of indi- 

 viduals within a species. 



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



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

 ing at time of hatching. 



Predaceous (pre da'shus) animal, one which preys on others. 



Predatism (pred'a tiz'm), the practice of one animal preying on another. 



Primordial (pri mor'di al), the first or primitive form. 



Proboscis (probos'is), an extension of the head or mouth parts. May be nose, 

 as in elephant; mouth parts, as of moth; or pharynx, as of planaria. 



Proctodeum (prol: to de'um), the pocket in the ectoderm ventral to the posterior 

 part of the enteron of the embryo; primordium of the anus. 



Proglottid (pro glot'id), one of the sections or individuals of the chain making 

 up the body of a cestode, such as the tapeworm. 



Pronephros (pro nef'ros), the first kidney structure to form in the developing 

 vertebrate. 



Pronucleus (pro nu'kle us), one of the two nuclei within a fertilized egg before 

 cleavage occurs. 



Propagation (prop a ga'shiin), the production of new individuals. 



Prophase (pro'faz), the preparatory stages of mitosis during which the forma- 

 tion occurs of spindle, spireme, and chromosomes. 



Proprioceptor (pro prio sep'ter), the receptor or end organ of the nervous sys- 

 tem located within a certain tissue receiving stimulations in reference 

 to bodily position or orientation. 



Prostate (pros'tat) gland, one of the male reproductive organs producing part 

 of the semen. 



Prostomium (pro sto'mi iim), portion of the anterior segment of annelids which 

 overhangs the mouth. 



Protein (pro'tein), one of the organic compounds found in protoplasm. It con- 

 tains the elements carbon, oxygen, hydrogen and nitrogen. 



Protoplasm (pro'to plaz'm), the living matter of which all organisms are com- 

 posed. 



Protopodite (pro top'o dit), the proximal section of the crustacean appendage. 

 It includes coxopodite and basipodite. 



Prototroch (pro'to trok), the band of cilia extending around the equatorial region 

 of trochophore larva. 



Protrusible (pro trob'si b'l), the ability to be put out or extended from the body. 



Proventriculus (pro ven trik'ulus), the anterior, secretory portion of the stom- 

 ach in certain animals, as the bird. 



Pseudopodia (su do po'dia), protoplasmic processes (false feet) formed by cer- 

 tain protozoans and used for locomotion. 



Ptyalin (tl'alin), the starch-digesting enzyme of saliva; a diastase. 



Pupa (pu'pa), the encased, inactive stage between the larva and adult condition 



in many insects and other animals. 

 Pyloric (pilor'ik), pertaining to the pylorus. 



Pylorus (pilo'rus), the junction of the posterior portion of the stomach with 

 the small intestine. 



