GLOSSARY. 441 



Ungulata. — Hoofed quadrupeds. 

 Unicellular. — Consisting of a single cell. 



Vascular. — Containing blood-vessels. 



Vermiform. — Like a worm. 



Vertebrata: or Vertebrate Animals. — The highest division of the 

 animal kingdom, so called from the presence in most cases of a back- 

 bone composed of numerous joints or vertebras, which constitutes the 

 centre of the skeleton and at the same time supports and protects 

 the central parts of the nervous system. 



Whorls. — The circles or spiral lines in which the parts of plants are 



arranged upon the axis of growth. 

 Workers. — See Neuters. 



Zoea-STAGE. — The earliest stage in the development of many of the higher 

 Crustacea, so called from the name of Zo'ia applied to these young 

 animals when they were supposed to constitute a peculiar genus. 



ZOOIDS. — In many of the lower animals (such as the Corals, Medusa;, &c.) 

 reproduction takes place in two ways, namely, by means of eggs and 

 by a process of budding with or without separation from the parent of 

 the product of the latter, which is often very different from that of the 

 egg. The individuality of the species is represented by the whole of 

 thaform produced between two sexual reproductions; and these forma, 

 which are apparently individual animals, have been called zooids. 



