GLOSSARY 449 



PROTOPODITE. The basal portion of the typical Crustacean ap- 

 pendage from which arise the endopodite and exopodite. 



PROTOZOA. Unicellular animals. 



PURE LINE. A group of individuals bearing identical genes, 

 derived from a common homozygous ancestor. 



PUTREFACTION. The simplification of nitrogenous compounds, 

 such as proteins, chiefly through the action of enzymes of living 

 organisms. See Fermentation. 



PYLORIC VALVE. Muscular constriction between stomach and 

 small intestine. 



RECAPITULATION THEORY. Doctrine that individual development 

 (ontogeny) repeats in abbreviated and modified form the develop- 

 ment of the race (phylogeny). So-called biogenetic law. 



RECESSIVE CHARACTER. See Dominant character. 



REDUCTION. The halving of the chromosome number during 

 maturation. Transformation of duplex into simplex group. 



REDUCTION DIVISION. The division during spermatogenesis and 

 oogenesis which separates synaptic mates and reduces the 

 chromosome number one half. The mechanism of segregation. 



REFLEXES. Relatively simple and essentially automatic responses. 

 Merge into instincts which are the most complex reactions 

 made without learning. 



REGENERATION. The power of replacement of parts which have 

 been lost through mutilations or otherwise. 



RENAL PORTAL SYSTEM. Blood ('impure') from posterior part of 

 the body to kidneys via renal portal vein. Oxygenated blood to 

 kidneys via renal artery. Thus in animals with the renal portal 

 system there is a double blood supply to the kidneys. Present 

 in Fishes, Amphibians, and Reptiles; vestigial in Birds; absent 

 in Mammals. 



REPRODUCTION. The power of living matter to reproduce itself. 

 Protoplasmic growth resulting in cell division. 



RESPIRATION. Essentially the securing of energy from food, involv- 

 ing the exchange of carbon dioxide for oxygen by protoplasm. 



RESPONSE. Any change in the activity of protoplasm, and therefore 

 of an organism as a whole, as the result of a stimulus. 



