GLOSSARY 367 



Arthropoda {ar thro-p' o da) . A phylum of animals, including the insects, Crustacea, 

 centipedes, etc. For definition see Chapter XII. 



Articulate (or iik' u late). To join; said of bones. 



Artificial parthenogenesis {ar' ti fish' al par' the no jen' e sis). The artificial stimula- 

 tion of an egg to develop without fertilization. 



Artiomorphes {ar' ti o mor' feez). A group of animals in Blainville's early classifica- 

 tion; it comprised the animals whose bodies are bilaterally symmetrical. 



Ascaris {as' ka ris). A genus of round-worms (Nemathelminthes) parasitic in 

 various animals. A. megalocephala {meg' a lo sef a la), parasitic in the intestine 

 of the horse. 



Ascidian {assid'ian). Any one of a number of degenerate Chordata, members of 

 the subphylum Tunicata, order Ascidiacea. 



Asexual (a seks' u al). Not involving germ cells nor fusion of nuclei ; said of repro- 

 duction, or of an individual employing such a mode of reproduction. 



Assimilation (as sim' i la' shun). The conversion of digested foods and other raw 

 materials into protoplasmic substances. 



Aster (as' ter). The star-hke figure composed of a centrosome and the radiating lines 

 about it; or the centrosome may be lacking. 



Astefoidea {as' te roi' de a) . A class of Echinodermata comprising the starfishes. 

 For definition see Chapter XII. 



Astral rays {as' tral raze'). The radiating fines surrounding a centrosome in a dividing 

 cell. 



Asymmetrical {a' sim met' ri kal). Not capable of being divided by a line or plane 

 into halves which are mirrored images of each other. 



As5mimetry (a sim' me tri). Absence of any kind of symmetry. 



Attraction-sphere {at trak' shun sfeer). A differentiated portion of the cytoplasm of 

 a cell, usualty lying near the nucleus, and t3'pically containing a central body 

 called the centrosome. The whole structure is associated with the process of cell 

 division. 



Auchenia {aw ke' ni a). The genus to which the llama and vicuna belong. 



Auditory {aw' di to ri). Pertaining to hearing ; applied to the nerve of hearing and the 

 sensory part of the inner ear. 



Auricle {aw' ri k'l). The anterior chamber of the heart in fishes, and one of the two 

 anterior chambers in higher vertebrates. 



Autonomic nervous system {aw' to nom' ik). Same as sympathetic nervous system. 



Aves (a' veez). A class of vertebrate animals comprising the birds. 



Avicularia {a vik' u la' ri a) . Individuals of a Bugula colony, each shaped like a 

 bird's head. 



Axial skeleton {aks' i al). The skull, vertebral column, ribs, sternum, and hyoid 

 apparatus of vertebrates. 



Axolotl {aks' o lot'l). The larval form of the tiger salamander Ambystomxi tigrinum 

 which reproduces while in the larv^al state. 



Axon {aks' one). A projection from a nerve cell which ordinarily conducts impulses 

 away from the body of the cell. 



Back cross \bak' kros'). A cross between an Fi individual and one of its parent types. 

 Bascanion (has ka' ni on). A genus of snakes, including the black snake or blue racer. 

 Belon, Pierre (be Ion'). French naturalist and traveler, 1517-1564. 



