508 APPENDIX 



Protozoology. The science of unicellular animals, or Protozoa. 



Pseudopodium. Temporary protoplasmic projections for locomotion, 

 feeding, etc., as in Amoeba. 



Pupate. Assumption of a quiescent stage (pupa), in the life history of 

 Insects with a 'complete' metamorphosis, during which the larva is 

 reorganized as an adult; e.g., chrysalis of a Butterfly and in cocoon 

 of a Moth. 



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 and Decay. 



Pyloric Valve. Muscular constriction between stomach and small intes- 

 tine. 



Pyrenoid. Portion of chloroplast specialized for starch formation. 



Recapitulation Theory. Doctrine that individual embryonic develop- 

 ment (ontogeny) repeats in abbreviated and modified form the de- 

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



Recessive Character. See Dominant Character. 



Recomrination. Heritable variation due to the typical reassortment of 

 the chromosomes during maturation and fertilization. Includes crossing- 

 over of genes. 



Reduction. The process in maturation, during spermatogenesis and 

 oogenesis, which separates synaptic mates and reduces the chromosome 

 number one-half. Meiosis. The mechanism of segregation. 



Reflex. A relatively simple and essentially automatic response resulting 

 from the transmission of a sensory impulse to a nerve center and its 

 immediate reflection as a motor impulse independent of volition. A 

 conditioned reflex is one established by training. 



Regeneration. The replacement of parts which have been lost through 

 mutilations or otherwise. 



Renal Portal System. Blood ('impure') passes from posterior part 

 of the body to kidneys by the renal portal vein; oxygenated blood 

 to kidneys by the 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. Proto- 

 plasmic growth resulting in cell division. 



Respiration. Essentially the securing of energy from food by oxi- 

 dation, involving the exchange of carbon dioxide for oxygen by 

 protoplasm. 



