GLOSSARY 523 



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



divided by several radial planes. 

 Radiant energy (ra'di ant ener ji), 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'shun), repetition in development of an individual 



organism of its phylogenetic history. 

 Redia (re'di a), 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. 

 Regeneration (re jen er a'shun), the replacement of mutilated parts or an entire 



animal from a portion of one. 

 Renal (re'nal), pertaining to the kidney. 

 Rennin (ren'in), an enzyme constituent of gastric juice of mammals and capable 



of coagulating the protein portion of milk. 

 Reproduction (re pro diik'shun), the production by an organism of others of its 



kind. 

 Respiration (res pi ra'shim), the exchange within an organism of oxygen enter- 

 ing the protoplasm and carbon dioxide leaving it. 

 Response (re spons'), the reaction of an organism to a stimulus. 

 Rete (re'te), a limited meshlike arrangement or network. 

 Reticulum (re tik'u lum), a fibrous or tubular network. 

 Retractile (re trak'til), that which can be withdrawn. 

 Retrogression (ret ro gresh'un), going behind or moving backward. 

 Rhabdites (rab'dits), special structures found interspersed among the epidermal 



cells of flatworms. 

 Rheotropism (re ot'ro piz'm), response of an organism to mechanical currents. 

 Roe (ro), ovary and eggs of fish. 

 Rudiment (roo'di ment), partially developed or embryonic structure; usually 



without function. 

 Rugose (rob'gos), possessing many ridges and folds. 

 Ruminants (rob'mi nants), animals which chew the cud. 



Saprophyte (sap'rofit), an organism which absorbs nonliving organic matter 



in solution directly through the surface of the body. 

 Sarcolemma (sar ko lem'a), the delicate membrane immediately enclosing the 



striated voluntary muscle cell. 

 Sarcoplasm (sar'ko plaz'm), the cytoplasm of muscle cells exclusive of the sar- 



costyles or fibrils. 

 Sarcostyles (sar'ko stils), cytoplasm fibrils in the structure of cytoplasm of 



voluntary muscle cells. 

 Schizogony (ski zog'6 ny), asexual reproduction. 



Sclerotic (skle rot'ik), the dense fibrous outer coat of the vertebrate eye. 

 Scolex (sko'leks), knoblike "head'.' on anterior proglottid of cestode. 

 Scute (skut), a plate on the ventral side of the body of the snake. 

 Sebaceous glands (seba'shus), small subcutaneous glands, usually connected 



with hair follicles. 

 Sedentary (sed'en ter i), unattached forms which remain in one place. 

 Semen (se'men), fluid which carries the spermatozoa in the males of most 



animals. 

 Seminal (sem'inal), pertains to semen. 

 Semipermeable membrane (sem i pur'me ab'l), one which permits the passage ot 



solvents through it but not solutes, unless they dissolve in the membrane. 

 Senescence (senes'ens), period of old age and its effects. 

 Septum (sep'tum), a wall dividing two cavities. 



