578 GLOSSARY 



prostomium (pro sto' mi um). A lobe overhanging the mouth of an earthworm which 

 functions as a lip; it is not considered a metamere; adj., prostomial. 



protective resemblance. A resemblance of an animal to its environment which tends 

 to make it inconspicuous. 



protein (pro' te In). An organic compound, containing carbon, hj'drogen, oxygen, 

 and nitrogen, and which is an essential constituent of protoplasm. 



proto- (pro' to). G.; first, primary. 



protoplasm (pro' to pLiz'm). The living substance; of very complex composition; 

 adj., protoplasmic (pro to plaz' mik). 



protrusible (pro troo' si b'l). Capable of being put out or protruded. 



proventriculus (pro v6n trik' u liis). The anterior glandular portion of the stomach, 

 or a dilation of the alimentary canal in front of the gizzard. 



pseudo- (sii' do). G.; false. 



pseudopodium (su d6 po' dJ iim). A temporary locomotor protrusion from the sur- 

 face of a cell. 



pter (t6r). G.; wing. 



ptyalin (ti' a lin). The enzyme in the saliva that changes starches to sugars. 



pulmonary (piil' mo na ri). Pertaining to the lungs. 



pulmonate (ptil' mo nat). Possessing lungs. 



pupa (pu' pa). The quiescent stage between larva and adult in insects with complete 

 metamorphosis; adj., pupal. 



Purkinje (poor kin' y6), Johannes E. Czechish biologist; 1787-1869. 



pylorus (pilo'rus). The opening from the stomach into the intestine; adj., pyloric 

 (pi lor' Ik). 



Radial (ra' dl ill) symmetry. Applied to an organism in which the body can be divided 



into a number of parts separated by radial planes. 

 Ray, John. Enghsh biologist; 1628-1705. 

 re- (re). L.; again. 

 reaction (re ak' shun). The response which follows the application of a stimulus to a 



living organism. 

 reason. As a basis for behavior, the ability to analyze previous experiences, perceive 



analogies, and by a logical process arrive at an abstract conception which may 



determine subsequent action. 

 recapitulation (re ka pit yu la' shtin) theory. The conception that stages passed 



through in the evolution of the race to which an animal belongs are repeated in 



the development of the individual. 

 receptor (resfp'tor). A sense organ serving for the reception of stimuli; also a 



solitary cell acting in the same fashion. 

 recessive (re ses' iv). One of a pair of allelomorphic characters which does not appear 



because of the dominance of the gene corresponding to the other of the pair. 

 rect (r6kt). L.; straight. 

 rectum. The terminal portion of the large intestine in higher vertebrates and also 



in some invertebrates; adj., rectal. 

 Redi (ra' de), Francesco. Italian naturalist; 1 6267-1697. 

 redia (re' di a). A stage in the development of a fluke; rediae are produced partheno- 



genetically in the sporocyst. 

 reduction. The halving of the number of chromosomes in the maturation period of 



gametogenesis. 

 Reese, Albert M. American zoologist, at University of West Virginia; 1872- . 

 reflex arc. A chain of cells which in the simplest form of the arc are three in number — 



a receptor neuron on the surface which receives a stimulus and passes the effect 



as an impulse to an adjustor neuron; this in turn passes it on to an effector cell 



that performs an appropriate act. 



