GLOSSARY 403 



Teleostomi {te' le os' to mi). A subclass of Pisces comprising the true fishes. They 



have a skeleton partly or wholly of bone and respire by means of gills. 

 Telolecithal {teV o les' i thai). Containing much yolk, crowded toward the vegetative 



pole; said of eggs. 

 Telophase {tel' o faze). The final phase of mitotic cell division, in which the nuclei 



are reconstructed. 

 Tentacle. One of a number of armlike projections from hydroids, Bryozoa, Nautilus, 



and other animals. Also one of certain elongated individuals of a siphonophore 



colony. 

 Termite. One of an order of insects called "white ants," but not really ants. 

 Terrapene iter' a pee' nee). A genus of turtles of the family Testudinidae. 

 Terrigenous {ter rij' e nus). Derived from the land; as applied to lake bottoms, 



composed of material washed in from the land, as distinguished from material of 



organic origin. 

 Tertiary {ter' shi a' ri). The single period of Cenozoic time. 

 Test. A hard outer covering, capsule, or shell; as of a sea urchin. 

 Testis. The organ in which the male germ cells are lodged and developed. 

 Testosterone {les ios' ter one). A hormone produced by the interstitial cells of the 



testis; it controls development of secondary sexual characters and sex behavior. 

 Testudinata {tes tu' di na' ta). An order of reptiles, comprising the turtles. 

 Testudinidae {les' tu din' i dee). A family of turtles. 

 Tetrad. A quadruple body formed, during the growth period in the ripening of 



germ cells, from the union of two chromosomes which at the same time become 



duphcated. 

 Thales {Iha' leez). Greek philosopher and astronomer who lived about 640-546 B.C. 

 Thamnophis {Iham' no fis) . A genus of garter snakes. T. butleri {but'leri); T. 



proximus {proks' i runs); T. sackeni {sak' en i); T. sauritus {saw ri' tus). 

 Theophrastus {the' o fras' tus) . Greek philosopher, founder of botany, who lived 



about 372-287 b.c. 

 Thermocline. A layer of water in a lake in which the temperature falls at least 1°C. 



for each additional meter of depth. 

 Thiamin {thi' a min). Vitamin Bi, the preventive of polyneuritis or beriberi. 

 Thoracic. Pertaining to the thorax or chest. 

 Thoracolumbar system. That part of the autonomic nervous system which centers 



in the middle portion of the spinal cord. Each organ controlled by the auto- 

 nomic system is innervated once from it. 

 Thorax. A middle portion of the body of many animals, between head and abdomen. 

 Thricozoa {Ihrik' o zo' a). A class of animals (hair animals) in Oken's early classifi- 

 cation. It comprised the mammals which Oken also called Ophthalmozoa. 

 Thrombase. An enzyme which brings about the conversion of fibrinogen into fibrin 



in the clotting of the blood. 

 Thromboplastin. A substance which converts prothrombase into thrombase in the 



clotting of the blood ; it is found in blood platelets and many cells. 

 Thymus. A ductless gland located near the gill clefts, or in the neck, or in the anterior 



part of the thorax in vaiious vertebrates. 

 Thyroid. A ductless gland located in the ventral part of the pharynx. 

 Thyroxin {thi roks' in). The hormone of the thyroid gland. 

 Tibia. The inner one of the two bones in the lower leg of vertebrates, except the 



fishes. 

 Tibiofibula. The fused tibia and fibula of some Amphibia. 

 Tibiotarsus. A compound bone in the leg of a bird, formed of the tibia and certain 



of the tarsal bones. 



