818 Appendix 



Autotomy (o -tot' o mi) (Gr. autos, self; tomos, cut off), self-mutilation of an 

 organism, as the loss of an appendage. 



Autotrophisni (o to-trof izm) (Gr. autos, self; trophe, nourishment), capable of 

 self-nourishment by using chemical elements for food. 



Autumnal coloration, colors produced in leaves by such pigments as antho- 

 cyanins, xanthophylls, carotenes, etc. 



Auxin (ok' sin) (Gr. auxein, to increase), plant hormone influencing growth. 



Auxospore (ox' o spor) (Gr. auxe, grow; sporos, spore), a reproductive cell in 

 diatoms, usually resulting from the fusion of two diatoms. 



Avoiding reaction, a somewhat fixed, protective behavior induced by adverse 

 stimuli. 



Axial gradient, an orderly arrangement of regions of different metabolic rates, 

 with the most active at the apical end and a decrease in this metabolic 

 rate as one goes toward the posterior end. 



Axial skeleton (L. axis, axis), the main axis of the skeleton to which the ap- 

 pendages are attached. 



Axis of polarity, an imaginary line extending from the anterior to the posterior 

 end of an organism; the pole known as the animal pole is at the anterior 

 end of the axis, while the pole with less activity, the vegetal, is at the pos- 

 terior end of the axis. 



Axis of symmetry, double metabolic gradients which run from the middorsal (mid- 

 ventral in invertebrates) region laterally and ventrally (dorsally in inverte- 

 brates). 



Axon (ak' son) (Gr. axon, axis), elongated process of a nerve cell for conducting 

 impulses away from the cell body (contrast with dendrite). 



Azygos (az'igus) (Gr. a, without; zygon, yoke or mate), an unpaired muscle, 

 vessel or process such as the single azygos vein. 



B 



Backcross, a cross between an individual of the first filial generation (Fi) with 

 one of the parental types. 



Bacteria (bak-ter'ia) (Gr. baktron, a stick), very small chlorophyll-less, single- 

 celled fungous plants, a number of which produce diseases, decay, fer- 

 mentation, and similar results, while others are beneficial. 



Bacteriophage (bak -ter' i o faj) (Gr. baktron, bacteria; phagein, to eat), living 

 substance which destroys bacteria. 



Barrier (bar' i er) (Fr. barriere, bar), any physical, chemical, or biologic object 

 which prevents natural migrations of organisms. 



Basal metabolism, release of energy due to the oxidation of a definite quantity of 

 food. 



Basidiomycetes (ba sid i o mi -se' tez) (Gr. basidium, base; mycetes, fungi), a 

 fungus which produces spores on a paddle-shaped base called a basidium. 



Basidiospore, a spore produced on a basidium. 



Behaviorism, the reaction of animals to their environment. 



Biceps (bi' seps) (L. bis, two; caput, head), having two heads or origins, as biceps 

 muscle of the arm. 



Biennial (bi -en' i al) (Gr. bi, two; annus, years), a plant which lasts two years 

 (seasons), producing only leaves the first season and flowers and seeds 

 the second. 



