266 



GENERAL ZOOLOGY 



or buoys. Although the colony reaches the height of two 

 inches, the individual polyps are microscopic in size. Each 

 polyp has about fourteen tentacles amply provided with net- 

 tling capsules, which aid in capturing small pelagic animals. 

 The mouth is at the center of the circles of tentacles 

 (Fig. 132, l) ; it opens directly into the gastrovascular cavity. 

 As the branches are terminated by feeding polyps, the cells 



of the branches are probably supplied 

 with food by the polyps nearest at 

 hand. 



Reproduction in Bougainvillia may 

 be a mere increase in the number of 

 polyps by a process of budding similar 

 to that described for Hydra. Occa- 

 2 sionally, however, a bud develops into 

 a structure totally different from an 

 ordinary polyp, and after a series of 

 stages indicated in Fig. 132, 2, 3, 4, 

 finally becomes separated from the 

 colony and floats away as a free- 

 swim mi 11 g individual (Fig. 133). 



FIG. 133. Medusa. Much This is callecl the ^edltsa stage of 



enlarged. (After Allman) the animal. The medusa has some- 



i, bell; 2, tentacle; .3, maim- thing like the shape of an umbrella. 



The mouth is located at the end of 

 the pendent manubrium (Fig. 133, 3). 

 The gastrovascular cavity sends out four slender tubes (Fig. 

 133, 4) radially to the perimeter, where a circular canal joins 

 them. Tentacles (Fig. 133, 2) stream downward from the mar- 

 gin, and at their bases are minute sense-organs (Fig. 133, 5). 

 There are male and female medusas. The ovaries and the 

 spermaries of Bougainvillia are located in the manubrium. 

 When the eggs and spermatozoa are ripe, they pass out 

 through the mouth, and fertilization takes place in the water 



brium; 4, radial tubes; 

 5, sense-organs 



