GLOSSARY 



Acquired character. — Any change in the body (soma) of an individua 

 due to change of function or change of environment. Same as Modification. 



Adaptation. — Any character, structural or functional, in an organism 

 that helps to enhance the fitness of that organism. 



Agamic reproduction. — See Asexual reproduction. 



Allelomorph. — One of a pair of contrasted characters; one of a pair of 

 genes (factors) determining the development of such characters, and be- 

 lieved to occupy equivalent loci in homologous chromosomes: a Mendelian 

 pair. 



Analogous structures. — Any two or more structures that subserve the 

 same function in the different kinds of animals or plants, but which arise 

 from different embryonic rudiments and have fundamentally different 

 structural constitutions. Contrast with Homologous structures. 



Anthropoid. — Literally, manlike; refers especially to the manlike apes. 



Apogamy. — A term used by botanists, synonymous with Partheno- 

 genesis. 



Asexual reproduction. — Any method of reproduction that does not in- 

 volve the union of gametes. (Some authorities consider parthenogenesis 

 as a phase of asexual reproduction.) 



Atavism, — The cropping out of ancestral characters in an individual. 



Atrophy. — The dwindling away of a structure in an individual or in a 

 race. 



Autosome. — .\ny chromosome other than those that are recognized as 

 especially involved in the heredity of sex. See Sex chromosome. 



Biometry. — That branch of biology that investigates organic differences 

 by statistical methods. 



Blastula. — An early embryonic stage consisting tj^Dically of a hollow ball 

 of cells. 



Castration. — The removal from an organism of the gonads (testes or 

 ovaries). 



Catastrophism. — The idea, held by Cuvier and others, that the geologic 

 strata were sharply marked off from one another because great catastrophies 

 had brought each era to an end, and that all life was destroyed in each 

 catastrophe. Contrast with Uniformitarianism. 



Cell. — The smallest unit of living substance that can exist in a free 

 state; the unit out of which tissues are composed. 



Centrosome. — An organ of a cell which seems to be a center of forces 

 that express themselves in mitotic cell division. 



Character. — One of many structural or functional details that character- 

 ize an individual or a race. 



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