GLOSSARY. 377 



Tkachka (Gr. tracheia, the roush windpipe). The tube which conveys air to 



the lungs in the air-breathing VerteWates. In Insects, MyriapoJs, and 



Spiders, the air -tubes whicli ramify througli the body. 

 Tremaxoda (Gr. trima, a pore or hole). An order of ticolecida. 

 Trilobita (Gr. treis, three ; loios, a lobe). Au extinct order of Crustacea. 

 TUBICOLA (Lat. tuha, a tube ; mlo, I inhabit). An order oi Annelida. 

 Tubulabida (Lat. tvha, a tube). Often used instead of Corynida to designate 



an order of the Hydrozoa. 

 TuNiCATA (Lat. Umica, a cloak). The Sea-squirts, a class of the Molliis- 



coida. 



Ulna (Gr. olene, the elbow). The outermost of the two bones of the fore-arm, 

 correspondiug with th^jibuM of the hind-limb. 



Umbo (Lat. the boss of the shield). The beak of a bivalve shell. 



Umbrella. The contractile disc of one of the Lucernarida. 



Ungulata (Lat. ungida, a hoof). The order of Mammalia comprising the 

 Hoofed Quadrupeds. 



Univalve (Lat. unus, one ; valixe, folding-doors). Applied to shells com- 

 posed of a single piece or valve. 



Urodela (Gr. oura, tail ; delos^ visible). The order of the " tailed " Am- 

 phibians. 



Vacuoles (Lat. vacuus, empty). The little cavities often formed in the in- 

 terior of many of the Protozoa by the i^resence of particles of food, sur- 

 rounded by a little water. Many vacuoles appear to be of a different nature, 

 being permanent cavities in the protoplasm, and being in some cases con- 

 tractile. 



Ventral (Lat. venter, the stomach). Relating to the inferior surface of the 

 body. 



Ventricle (Lat. ventriculus, diminutive of venter, belly). One of the cavities 

 of the heart. 



Vermes (Lat. vermis, a worm). Sometimes used at the present day in the , 

 same, or nearly the same, sense as Hcolecida, or as Scolecicla plus the 

 A narthropoda. 



Vermiform. Worm-like in shape. 



Vertebra (Lat. verto, I turu). One of the bones composing the spinal column 

 or backbone. 



Vebtebrata. The sub-kingdom comprising animals almost all of which have 

 a more or less well-developed vertebral column. 



Vesicle (Lat. vesica, a bladder). A little sac, bladder, or cyst. 



Viscera (Lat. viscus). The internal organs of the body. 



Viviparous (Lat. vivus, alive; and ^ario, I bring forth). Applied to animals 

 which bring forth their young alive. 



XiPHOSURA (Gr. xiphos, u sword ; aura, tail). An order of Crustacea com- 

 prising the King crabs. 



ZobiD (Gr. zoSn, animal ; eidos, form). The more or less completely inde- 

 pendent organisms produced from a primitive being by gemmation or 

 fission, whether these remain attached to one another or are detached and 

 set free. 



Zoophyte (Gr. soSn, animal ; pliuton, plant). Loosely applied to many 

 plant-like animals, such as Sponges, Corals, Sea-anemones, Sea-firs, Sea- 

 mats, &c. 



