COMPOSITE ANIMALS. 97 



is by gemmation, or budding. A small swelling or 

 protuberance is observed within the interior mem- 

 brane or sac near the apparent orifice whence the 

 tentacles are protruded. This protuberance gradu- 

 ally increasing in size, at length assumes the exact 

 form of the parent ; and though still connected 

 with it, yet commences life on its own individual 

 account, and reproduces itself in like manner. A 

 connected colony is thus formed, branching off in 

 all directions, like the little twigs of a tree. At 

 every joint there is a partial division ; so that each 

 little branchlet contains its own individual polypide, 

 as in a cell or chamber, while still united to its 

 nearest neighbour. In this way the colony is 

 formed; and hence the name Polyzoa i.e., many- 

 lives, or compound animal is derived. In some 

 genera this process is carried still further, and a 

 second division is produced as in Cristatella and 

 Lophopus where, when the colony becomes un- 

 wieldy, a separation, not of the individuals as such, 

 but of the colonial structure, takes place : the reason 

 of these exceptions being apparently because of the 

 more delicate and softer nature of the investing 

 membranes in these than in other forms. 

 H 



