III. GLOSSARY 



A biogenesis. The abandoned idea that living matter may arise at the 

 present time from the non-living without the influence of the former. 

 See Biogenesis. 



Absorption. The passage of nutritive and other fluids into living cells. 



Acoelomate. Not possessing a coelom, or body cavity; e.g., Hydra. See 

 Enterocoela. 



Acquired Character. A modification of body structure or function 

 which arises during individual life. 



Adaptation. The reciprocal fitness of organism and environment; a 

 structure or reaction fitted for a special environment; the process by 

 which an organism becomes fitted to its surroundings. 



Adrenal Glands. Ductless glands situated near the kidneys. Secretion 

 supplies the hormones adrenaline and cortin. 



Aerobe. An organism requiring free oxygen. See Anaerobe. 



Afferent Root. Dorsal, or posterior, root of certain cranial and all 

 spinal nerves through which sensory nerve impulses enter the brain and 

 spinal cord. See Efferent Root. 



Alrino. An individual lacking normal pigment, e.g., a white rat. Al- 

 binism in the Rat and Man is a typical Mendelian recessive character. 



Algae. A heterogeneous group of lower plants in which the body is uni- 

 cellular or consists of a thallus; e.g., Protococcus, Spirogyra, Seaweeds. 



Allantois. An embryonic membrane of higher Vertebrates, chiefly res- 

 piratory in function. 



Allelomorphs. Alleles. Genes similarly situated on homologous chromo- 

 somes. Homologous genes. See Homologous Chromosomes. 



Alternation of Generations. Typically the alternate succession of sex- 

 ual and asexual generations in the life history; e.g., Obelia. 



Alternative Inheritance. See Dominant Character. 



Amino Acids. Components of proteins. Organic acids in which one hydro- 

 gen atom is replaced by the amino group (NH 2 ). 



Amnion. A delicate membrane enclosing the developing embryos of 

 Reptiles, Birds, and Mammals. 



Amoeboid. Usually applied to the flowing movements of a cell, as in 

 Amoeba and white blood corpuscles. 



Amphimixis. The mingling of the germ plasm of two gametes in the zygote. 



Anabolism. The constructive phase of metabolism. See Katabolism. 



Anaerobe. An organism not requiring free oxygen; e.g., certain Bacteria 

 and parasitic Worms. See Aerobe. 



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