GLOSSARY 525 



Syngamy (sin'ga mi), union of mature gametes to form a zygote. 

 System (sis'tem), an aggregation of organs to perform some general function 

 of life. 



Taxis (tak'sis), a tropismal response involving movement of an organism as a 

 whole. 



Taxonomy (taks on'6-mi) (systematic zoology), the classification or orderly ar- 

 rangement of organisms according to their natural surroundings. 



Tegumentary (tegumen'ta ri), referring to the skin. 



Telencephalon (tel en sef'a 15n), the anterior division of the vertebrate brain. 



Telolecitlial (tel 6 les'i thai), type of egg with abundant yolk unequally dis- 

 tributed. 



Telophase (tel'o faz), the final stage in mitotic divisions. 



Tentacle (ten'tak'l), flexible, armlike extension of the body of many non- 

 chordates. 



Terrestrial (ter res'tri al), a land form; living on or in the ground. 



Testis (tes'tis), male gonad. 



Thermotropism (ther mot'ro piz'm), response of an organism to temperature. 



Thigmotropism (thig mot'ro piz'm), response of an organism to contact. 



Thoracic (tho ras'ik), of or pertaining to the thorax or chest. 



Thorax (tho'raks), the middle region of the body. 



Threshold (thresh'old), the minimum strength of stimulus necessary to get a 

 response. 



Thrombin (throm'bin), the substance of the blood which plays an important 

 part in clotting. 



Thyroxin (thi rok'son or -sin), the hormone which is produced by the thyroid 

 body. 



Tissue (tish'ii), an organization of similar cells into a layer or group for the 

 perfoi'mance of a specific fifnction. 



Toxin (tok'sin), any poisonous substance. 



Trachea (tra'kea), the windpipe or a tube for conveying air to the lungs; air 

 tubes in insects. 



Trichocyst (trik'6 sist), saclike structure in the ectosarc of Paramecium. 



Triploblastic (trip 16 blas'tik), composed of three germ layers. 



Trivium (triv'ium), the three anterior ambulacra of Echinodermata, collec- 

 tively. 



Trochophore (trok'o for), a semispherical type of larva with cilia; found among 

 flatworms, annelids, mollusks, etc. 



Tropism (tro'piz'm), the movements of an organism in response to a stimulus. 



Trypanosome (trip'a no s6m), genus of parasitic Protozoa (Mastigophora) in- 

 cluding the causal agent of African sleeping sickness. 



Trypsin (trip'sin), a pancreatic enzyme which converts proteins to amino acids. 



Tsetse (tset'se) fly, a species of fly which serves to transmit the causal agent 

 of African sleeping sickness. 



Tundra (tobn'dra), level plains region of the arctic region. 



Tympanum (tim'paniim), cavity of the" middle ear or more generally any organ 

 serving to receive sound waves. 



Umbilical (umbil'ikal) cord, the cordlike connection between the fetus and 

 the placenta. 



Umbilicus (iim bil'i kus), the navel or the point of attachment of the umbilical 

 cord to the abdomen. 



Uncinate (lin'sinat), in the shape of a hook. 



Ungulate (img'gulat), hoofed. 



Unguiculate (un gwik'lat), having claws. 



Urea (iire'a), a nitrogenous compound which is produced as a protein by- 

 product in metabolism. 



Ureter (iire'ter), the duct which conveys urine from the metanephric kidney 

 to the cloaca or bladder. 



