Appendix 817 



Artery (ar'teri) (Gr. arteria, artery), vessel conducting blood away from the 



heart. 

 Arthropoda (ar -throp' o da) (Gr. arthron, jointed; pons, appendage), phylum of 



animals with jointed appendages but without notochord or vertebral column. 

 Artificial parthenogenesis (par the no -jen' e sis) (Gr. parthenos, virgin; genesis, 



orgin), the artificial activation of an egg to develop without fertilization 



by a male sperm. 

 Artificial selection, the development of certain traits by artificially crossing se- 

 lected individuals. 

 Ascocarp (as'kokarp) (Gr. askos, sac; karpos, fruit), a structure which produces 



saclike asci in sac fungi. 

 Ascomycetes (as ko mi -set' ez) (Gr. askus, sac; mycetes, fungi), higher fungi 



whose spores are formed in saclike asci. 

 Ascospore (as' ko spor) (Gr. askus, sac; sporos, spore), a spore contained in a 



saclike ascus. 

 Asexual (a -sek' shu al) (Gr. a, without; sexus, sex), reproduction without sex 



cells. 

 Assimilation (as sim i -la' shun) (L. ad, to; similare, to make Hke), conversion 



of digested food into living protoplasm. 

 Association areas, regions of the brain in which higher mental processes are 



presumably affected. 

 Aster (as'ter) (Gr. aster, star), starlike figure of radiating lines about the cen- 



trosome during certain stages of animal cell mitosis. 

 Asymmetry (a -sim' e tri) (Gr. a, not; symmetria, symmetry), without symmetry. 

 Atlas (at' las) (Gr. Atlas, name of a god whose pillars upheld the heavens), the 



first or anterior vertebra of the neck. 

 Atom (at'um) (Gr. atomos, indivisible), structural unit of a molecule which 



maintains its integrity in a chemical change; an atom enters into, and 



issues from, a chemical reaction unchanged except for a loss or gain of 



electrons. 

 Atomic theory, all matter is made of small units called atoms. 

 Atrophy (at'rofi) (Gr. a, not; trophe, nourishment), wasting away of an organ 



or a part of it (contrast with Hypertrophy). 

 Attraction sphere (L. attr actus, draw to), structure which may aid in attracting 



chromosomes toward the cell poles during mitosis. 

 Auditory (o' di to ri) (L. audire, to hear), pertaining to sound reception and 



interpretation. 

 Autogamy (o -tog' a mi) (Gr. autos, self; gamos, marriage), nuclear reorganiza- 

 tion and self-fertilization within the same individual (example, Paramecia). 

 Autolysis (o-tol'isis) (Gr. autos, self; lysis, destroying), self-digestion of a tissue 



or organ by enzymes formed by it. 

 Autonomic system (oto-nom'ik) (Gr. autos, self; nomos, law), a system of 



nerves and ganglia regulating involuntary muscles, blood vessels, etc., 



and connected with the central nervous system by the cranial and spinal 



nerves. 

 Autosome (o' to sum) (Gr. autos, self; soma, body), a regular chromosome as 



distinguished from a sex chromosome, 



