PLANT-ANIMALS, OR ZOOPHYTES. 159 



to which our attention has hitherto been confined, are 

 neuters, they are the workers of the colony, and, in. 

 some sense, correspond to the " workers " in a hive of 

 bees. Now that we are required to describe the 

 method in which new colonies are formed, and 

 account for the perpetuation of the species, we must 

 discover other members of the colony than those 

 fixed, or permanent individuals, which furnish the 

 colony with material support. The polypes are pro- 

 duced only at certain seasons, and occupy different 

 positions in different species. They are produced 

 in buds of a peculiar structure, borne upon an off- 

 shoot from one of the branches, and enclosed in a 

 sort of urn, or receptacle, formed from the same 

 chitinous, or horny, material as the covering, or 

 skeleton of the colony. There may be some species 

 in which this method does not prevail, in all its par- 

 ticulars, but in the most common species it is 

 sufficiently general for our purpose. 



The sexual bud (gonophore) consists of an outer 

 coat, which serves for protection, and an enclosed, 

 either male or female, zooid. Sometimes male and 

 female occur on the same shoots, but in some cases 

 they are produced on different colonies of the same 

 species. The sexual zooids, which are in time 

 developed from the special sexual buds, are either 

 fixed to the colony, as the working polypes are, or 

 they become free, and float away from the parent 



