GLOSSARY-INDEX 423 



tympanic membrane (Gr. tympanum = a drum) . The membrane cover- 

 ing the ear cavity and serving to collect the air waves, 175, 197. 



tympanum (Gr. tympanum = a drum) . The cavity of the middle ear, 

 197. 



TYNDALL, 14. 



typhlosole (Gr. typhlos = blind + solen = a tube). A cylindrical rod ex- 

 tending through the intestine of the earthworm, 158. 



typhoid fever, 232. 



ulna, 182. 



Ulothrix, 93, 136. 



unicellular organisms. Organisms made of single cells, or of colonies of 

 similar cells, each of which can carry on all the functions of life, 52, 

 90. 



unit characters. Characters that are inherited as units, 359. 



urea. An excretion from animals containing the nitrogen waste 

 (CH 4 N 2 O), 210. 



ureter. The duct carrying urine from the kidney to the bladder, 199. 



urethra. The duct carrying the urine from the bladder to the exterior, 

 199. 



urogenital organs (Gr. ouron = urine + Lat. genitalis = genital). The ex- 

 cretory and sexual organs, which, in vertebrates, are united, 201. 



urostyle (Gr. oura = tail + stylos = a pillar). The single bone in the frog 

 which represents the tail, 177. 



use and disuse, LAMARCK'S theory of, 351. 



uterus. A chamber in the oviduct where the eggs are stored, or in mam- 

 mals where the embryo develops, 200, 291. 



vacuoles (Lat. vacuum = a cavity). Spaces inside the body of cells, 

 usually filled with a clear liquid, 37. 



vagus. A branch of the pneumogastric nerve extending to the heart. 



valves. Membranous folds in the vessels or in the heart, which allow 

 liquid to flow only in one direction, 188. 



variability. The quality of showing variations. 



variations. Slight differences between animals of the same species, 261, 

 327. 



varieties. See subspecies. 



vasa deferentia (Lat. vasa = vessel + deferens = carrying down). -The 

 ducts that carry sperms from the spermary to the exterior, 164, 

 250. 



vasa efferentia (Lat. vasa = vessel + efferens = carrying to). The ducts 

 carrying sperms from the sperm aries to the kidney in the frog. 



vegetative functions. Those possessed by vegetables as well as animals, 

 associated with alimentation and reproduction, 217. 



