322 GLOSSARY. 



Vebtebrata : or Vertebrate Animals. — The highest division of 

 the animal kingdom, so called from the presence in most 

 cases of a backbone composed of numerous joints or vertebrcB, 

 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-staoe. — The earliest stage in the development of many of 

 the higher Crustacea, so called from the name of ZoSa 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, Medusae, 

 &e.) 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 the form produced be- 

 tween two sexual reproductions ; and these forms, which are 

 apparently individual animals, have been called zooids. 



