GLOSSARY . 335 



numerous joints or vertebrce, which constitutes the centre 

 of the skeleton and at the same time supports and pro- 

 tects 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 Zoea 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, etc.) 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 between two sexual 

 reproductions; and these forms, which are apparently 

 individual animals, have been called zooids. 



