664 



COLLEGE ZOOLOGY 



A-quat'ic (L. aquaticus, living in water). Of 

 or pertaining to water. Living in water. 



Aq'ue-duct (L. aqua, water; ducere, to lead). 

 A canal or channel for conduction of a fluid; 

 used especially for specialized lymph passages 

 in the brain, not for lymphatics in general 

 nor for blood vessels. 



A-rach'noid (Gr. arachnes, spider; eidos, 

 form ) . The arachnoid membrane; the cen- 

 tral of the three meninges covering the 

 vertebrate brain and spinal cord. It is very 

 fine and delicate. 



Ar-bo're-al (L. arbor, tree). Pertaining to trees, 

 as tree-living. 



Ar-chen'ter-on (Gr. arche, beginning; enteron, 

 gut). The primitive digestive tract of a 

 metazoan embryo, formed during gastrula- 

 tion. 



Ar'ter-y (L. arteria, windpipe, artery). A blood 

 vessel which carries blood away from the 

 heart. 



Ar'thro-pod (Gr. arthron, joint; pous, foot). 

 An invertebrate animal with jointed appen- 

 dages, like crayfish, insects, etc. 



Ar-tic'u-la-tion (L. articulus, joint). A joint as 

 between two segments or structures. 



Ar'ti-fi"cial clas'si-fi-ca"tion (L. ars, artis, art; 

 facio, make. L. classis, division). Classifica- 

 tion based on characters of convenience 

 without relation to evolutionary (phylogene- 

 tic) significance. 



Ar'y-te^'noid (Gr. arytaina, pitcher). Pertaining 

 to a pair of laryngeal cartilages that lie pos- 

 terior to the thyroid cartilage. 



A-se.x'u-al re-pro-duc'tion (L. a, not; sexus, sex. 

 L. re, again; productio, production). Repro- 

 duction not involving gametes (sperms or 



eggs)- 



As-sim'i-Ia'tion (L. ad, to; similis, like). The 

 changing of digested foods and other mate- 

 rials into protoplasm. 



As'ter (Gr., star). A starlike figure formed 

 during mitosis and composed of the centro- 

 some and the lines radiating from it. 



A-sym'me-try (Gr. a, without; syn, with; 

 inetron, measure). The condition in which 

 opposite sides of an animal are not alike; 

 without symmetry. 



At'a-vism (L. atavus, ancestor). Resemblance 

 to a remote ancestor. 



At'las (Gr., giant). The first cervical vertebra; 

 the first vertebra upon which the skull rests. 



At'oU (Maldiv'ian, atolu). A horseshoe or 

 ring-shaped island or islands consisting of a 

 belt of coral reef surrounding a central 

 lagoon. 



A'tri-al cav'i-ty (L. atrium, central room. L 

 cavus, hollow). A cavity in protochordates 

 and some caudate larvae (e.g., tunicates, am- 

 phioxus, frog tadpoles) through which water 

 passes after moving out of the gill slits. 



A'tri-o-pore (L. atrium, central room; porus, 

 channel). The exterior opening from the 

 atrial cavity in the amphioxus. 



A'tri-um ( L. atrium, chamber ) . A chamber or 

 cavity; the term may refer to the atrium of 

 the heart or to the specialized outer cavity 

 of the amphioxus. 



At'ro-phy (Gr. a, not; trephein, to nourish). 

 A wasting away or withering of the body, 

 or of any of its parts. 



Au'di-to-ry (L. audire, to hear). Pertaining to 

 the organ or sense of hearing, as the eighth 

 cranial ner\'e. 



Au-to-nom'ic (Gr. autos, self; nomos, law), 

 independent; self-governing. 



Au-to-nom'ic nerv'ous sys'tem (Gr. autos, self; 

 nomos, law. L. nervosus, sinewy, vigorous. 

 Gr. systema, a placing together). A system 

 of ganglia and nerves controlling the invol- 

 untary actions of the body; the action of the 

 ductless glands, viscera, blood vessels, and 

 all organs containing involuntary muscle, 

 and communicating with the central nervous 

 system by way of the roots of the spinal and 

 cranial nerves. 



Au'to-some (Gr. autos, self; soma, body). Any 

 chromosome except a sex chromosome. 



Au-tot'o-my (Gr. autos, self; tome, cutting). 

 Self-mutilation; the automatic "voluntary" 

 breaking off of a part of the body of an 

 animal. 



Ax'i-al gra'di-ent (L. axis, axle. L. gradus, 

 step). Gradation of the rate of metabolism 

 along the length of a principal axis of an 

 animal. 



Ax'i-al skere-ton. That part of the vertebrate 

 skeleton which consists of the skull, verte- 

 brae, sternum, and ribs. 



Ax'is ( L. axis, axle ) . The second cervical verte- 

 bra. A line such as the anteroposterior axis 

 of the body, around which parts are sym- 

 metrically arranged. 



Ax'is cyl'in-der (L., axle. Gr. kylindros, from 



