918 TEXTBOOK OF ZOOLOGY 



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 (prok 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 bod.y of a cestode, such as the tapeworm. 

 Pronepliros (pr6 nef'ros), the^ first kidney structure to form in the developing 



vertebrate. 

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



cleavage occurs. 

 Propagation (prop a ga'shun), 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 pri 6 sep'ter), the receptor or end organ of the nervous 



system 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 



contains 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'sib'l), the ability to be put out or extended from the 



body. 

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



stomach in certain animals, as the bird. 

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



certain protozoans and used for locomotion. 

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

 Pupa (piVpa), 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'riis), the junction of the posterior portion of the stomach with 



the small intestine. 



Radial symmetry (ra'dial sim'etri), applied to a body that can be equally 



divided by several radial planes. 

 Radiant energy (ra'diant enerji), inherent power or energy transmitted 



through space, as that from the sun, radium, or x-ray. 

 Radula (rad'ula), the sheetlike rasping structure of the mouth of gastropods; 



used in mastication of food. 

 Recessive (reses'iv), in reference to a gene which is carried in the cell without 



expressing its character unless there is absence of its dominant mate. 

 Recapitulation (re kapit u la'shiin), repetition in development of an individual 



organism of its phylogenetic history. 

 Redla (re'dia), second phase of the life history of the fluke. 

 Reflex (re'fleks) action, automatic reaction to a stimulus from a receptor 



neuron and passed on to an adjustor neuron; performs an involuntary, 



appropriate act. 



