688 



COLLEGE ZOOLOGY 



Tel'son (Gr., a boundary). A terminal exten- 

 sion of the last abdominal appendage of a 

 crustacean such as the crayfish. 



Tea'don (L. tendere, to stretch). The tough, 

 cordlike connective tissue extension at the 

 end of a muscle which attaches it to other 

 structures. 



Ten'ta-cle (L. tentare, to touch, feel). A flex- 

 ible, armlike extension from the body of 

 many nonchordates, such as the hydra; used 

 in grasping and movement. 



Ter'gum (L., the back). The dorsal portion of 

 the exoskelcton of any body segment in the 

 arthropods, such as the grasshopper. 



Ter-res'tri-al ( L. terra, earth ) . Living on the 

 ground. 



Tes'tis (L. testis). Male reproductive gland 

 (gonad), in which sperms are formed. 



Tet'rad (Gr. tetra, four). A group of 4 chro- 

 matids which appears during maturation, the 

 product of a pair of homologous chromo- 

 somes. 



The'o-ry (Gr. theoria, a beholding, specula- 

 tion ) . A possible explanation of natural phe- 

 nomenon for which there is some evidence 

 but not enough for proof. 



Ther'mo-tax"is (Gr. therme, heat; taxis, re- 

 sponse). The behavior response of an or- 

 ganism to heat or cold. 



Ther-mot'ro-pism (Gr. therme, heat; trope, 

 turning). The behavior response of an or- 

 ganism to heat. 



Thig-niot'ro-pism (Gr. thigma, touch; trope, 

 turning). The behavior response of an or- 

 ganism to contact. 



Tho-rac'ic (Gr. thorax, chest). Pertaining to 

 the thorax or chest. 



Tho'rax (Gr., chest). The major division of 

 an animal just posterior to the neck, or head, 

 if no neck is present. 



Thy'mus (Gr. thymos, thymus). A two-lobed 

 organ located just below the thyroid of mam- 

 mals. 



Thy'roid (Gr. thyreos, shield; eidos, form). 

 An endocrine gland in the neck of verte- 

 brates, which exerts an influence on growth 

 and metabolism. 



Thy-rox'ine. The hormone secreted by the 

 thyroid gland. 



Tib'i-a L. tibia, pipe). The larger medial bone 

 of the vertebrate lower leg; the part between 

 the femur and tarsus in insects. 



Tis'sue (L. texere, to weave). A group of cells 

 of similar structure, with intercellular sub- 

 stances, if any, which perform a specialized 

 function. 



Tis'sue flu'id. The extracellular fluid which 

 constitutes the environment of the body 

 cells. 



Tox'in (Gr. toxicon, poison). A poisonous 

 product of animal or plant origin. 



Tra'che-a (Gr. tracheia, windpipe). The wind- 

 pipe of vertebrates; an air tube in breathing 

 arthropods. 



Trait ( L. tractus, a drawing ) . A term loosely 

 used by geneticists as a synonym of "char- 

 acter." 



Trans-verse' proc'ess (L. trans, across; vertere, 

 to turn. L. procedere, to go before). One of 

 the lateral projections of a vertebra. 



Trich'o-cysts (Gr. trichos, hair; kystis, blad- 

 der) . One of the definite bodies lying in the 

 ectoplasm and producing hairlike fibers in 

 such animals as the paramecium. 



Tri-gem'i-nus (L. trigeminus, born three to- 

 gctlier). Fifth cranial nerve. 



Trip'lo-blas"tic (Gr. triplax, triple; blastos, 

 bud). Derived from the 3 primary' germ 

 layers — ectoderm, mesoderm, and endoderm. 

 The embryonic tissue is not always in the 

 form of a layer, but sometimes consists of 

 groups of cells. 



Tro-clian'ter (Gr. trechein, to run). The sec- 

 ond segment of the insect leg between the 

 coxa and the femur. 



Tro'pho-zo"ite (Gr. trophe, from trophein, 

 nourishment; zoion, living being, animal). 

 An endozoic protozoan in the phase of its 

 life cycle where its principal activity is nu- 

 trition and growth. 



Tro'pism (Gr. trope, turning). The automatic 

 response of an animal to a particular stimu- 

 lus. 



Tube feet (L. tuba, pipe. A.S. jet, feet). Tubu- 

 lar organs of locomotion found in the ambu- 

 lacral grooves of starfishes and some other 

 echinoderms. 



Tym-pan'ic mem'brane (Gr. tyinpanon, ear- 

 drum. L. membrana, skin covering). The 

 eardrum. 



Typh'lo-sole (Gr. typhlos, blind; solen, chan- 

 nel). A median dorsal internal fold in the 

 intestine of several types of animals, includ- 

 ing the earthworms. 



