GLOSSARY 409 



Tube-feet (tube' feet'). Tubular protrusions from the arms of echinodcrms, which 

 serve as organs of locomotion. 



Tuberculate (tu her' ku late). Bearing cusps or conical prominences; said of teeth. 



Tubifex {tu' hVfeks). A genus of freshwater annelid worms. 



Tubular gland {tu' bu ler). A gland whose lumen is of about uniform bore throughout. 



Tunic {Ixi' nik). An enveloping membrane or test. 



Tunicata {tu' ni ka' to). A subphylum of Chordata, including the sea-squirts, sea- 

 pork, salpas, etc. For definition see Chapter XII. 



Turbellaria {tur' hel la' ri a). A class of Platyhelminthes, ciliated flatworms leading 

 a free existence. 



Tyndall, John {tin' dal). British physicist, 1820-1893. 



Type {tipe). In systematic zoology, an individual or group which is formally held 

 to be typical of the species or larger group to which it belongs; as, the type speci- 

 men of a species, the type species of a genus, or the type genus of a family. 



Typhlosole {tif lo sole). A ridge resulting from the infolding of the dorsal intestinal 

 wall of the earthworm. 



Ulna {uV na) . The bone on the httle finger side of the fore arm in Amphibia and the 



higher vertebrates. 

 Umbilical cord {umbil'ikal kord'). A rope-like cord in which blood vessels pass 



between an embryo and the placenta in viviparous animals. 

 Umbrella {urn breV la). The curved or cup-like body of a medusa. 

 Ungulata {ung' gu la' ta). A group of mammals to which the hoofed animals (pigs, 



sheep, horses, elephants, etc.) belong. 

 Ungulate {ung' gu late). One of the Ungulata. 



Xiraiorraiia.na.TiisTa iu' nifor' mita' ri aniz'm). The doctrine that geological proc- 

 esses of the past were similar to those of the present time. 

 Unio {u' ni o). A genus of freshwater mussels. 

 Unisexual {u' ni seks' u al). Involving but one sex, the female; appUed to partheno- 



genetic reproduction. 

 Unit character {u' nit kar' ak ter). A hereditary trait that behaves as a unit in trans- 

 mission, being capable of inheritance independently of other unit characters. 

 Universal symmetry {u' ni ver' sal sim' me tri). An arrangement of the parts of an 

 object or organism such that it is capable of being divided into symmetrical 

 halves by an indefinite number of planes passing in any direction through a 

 central point. 

 Urea {u re' a). A substance, CO(NH2)2, produced by the decomposition of proteins 



and some other substances in organisms. 

 Ureter {u re' ter) . A tube conducting urine away from the kidney. 

 Urethra {u re' thra). The duct by which urine is discharged from the bladder. 

 Urinary bladder {u' ri na ri blad' der). A bag in which urine is stored. 

 Uriniferous tubule {u' ri nif er us tu' bule). One of many coiled tubes making up the 



bulk of the kidney in vertebrates. 

 Urinogenital system {u' ri no jen' i tal sis' tern). A group of organs concerned 



with both excretion and reproduction in vertebrates. 

 Uroglena {u' ro gle' na) . A genus of flagellate Protozoa in which free-swimming spheri- 

 cal colonies are embedded in a gelatinous substance. 



