GLOSSARY 



NOCTURNAL. Pertaining to the night. CJ. DIURNAL. 



NOTOCHORD. A eellular c-ord formed between the archenteron and the neural tube 



during the early development of all chordates; the vertebral column is formed 



around but not from the notochord in vertebrates. 

 NUCLEUS (/V. NUCLEI). Fhe part of the cell containing chromatin and limited bv 



th(^ nuclear membrane. 

 NUTRITION. The science of foods; the basic processes or manner of obtaining foods. 

 NYMPH. An immature postembryonic stage in the life cvcle of a paurometabolous 



insect. 



OBLIGATE. Refers to conditions or processes required for the life of an organism; for 

 example, an organism that cannot live in the presence of atmospheric oxygen is 

 spoken of as an obligate anaerobe. Cf. FACULTATIVE. 



OLFACTORY. Pertaining to the sense of olfaction, or smell. 



OMNIVOROUS. Feeding upon both plants and animals. Cf. CARNIVOROUS and 

 HERBIVOROUS. 



ONTOGENETIC. Related to the origin and development of the individual. CJ. 

 PHYLOGENETIC. 



OOGENESIS. IhediiTerentiationoftheova. CJ. SPERMATOGENESIS. 



OPHTHALMIC. Pertaining to the eye. 



OPTIC. Pertaining to vision or to the eye. 



OPTIMUM. Conditions of temperature, salinitv, pH, humidity or any other environ- 

 mental factor under which an organism performs its vital functions with maxi- 

 mum efficiency. 



ORAL. Pertaining to the mouth, or place of ingestion. 



ORDER. One of the subdivisions of a class; a group of next higher rank than a 

 family. 



ORGAN. A group of tissues associated together for the performance of a special 

 function. CJ. SYSTEM. 



ORGANIC. Pertaining to organisms or resulting from their activities; in chemistry, 

 ( ompounds containing carbon. 



ORGANIC EVOLUTION. The process of descent with modification as a result of which 

 present-day species of animals have arisen from tho.se of the past. CJ. 

 EVOLUTION. 



ORGANISM. An animal or plant. 



ORGAN SYSTEM. See SYSTEM. 



OSTIUM. An opening or entrance. 



OVARY. A gonad in which ova undergo diflferentiation. Cf. TESTIS. 



OVIPAROUS. Egg-laying; producing young that develop from eggs which hatch 

 outside the body of the mother. CJ. OVOVIVIPAROUS and VIVIPAROUS. 



OVOVIVIPAROUS. Producing young that develop from eggs which hatch within the 

 l)od\- of the mother. CJ. OVIPAROUS and VIVIPAROUS. 



OVULATION. The discharge of eggs from the ovary. 



OVUM {fil. OVA). A mature or differentiated female germ cell; a macrogamete. 

 (J. SPERMATOZOON. 



PALEONTOLOGY. The study of structure, probable interrelationships, and distribution 

 of animals now extinct and known only through their fossil and other remains. 



PALP. A feeler. 



PAPILLA (/?/. PAPILLAE). A rounded, thick process or extension. 



PARAMYLUM. A starch-like carbohvdrate svnthesized and stored in manv plant-like 

 (laL^rclJate protozoans. 



PARASITE. An organism that lives in or on another, at the expense of the latter. 

 CJ. HOST. 



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