Introduction to Animal Morphology* \ 13 



Fission may also occur, and may be imperfect, vertical, 

 producing caespitose, or horizontal, producing la- 

 mellar masses. Buds may also form, and may be 

 basogenic (from the base of the parent), stoloniferous 

 (from basal stolons), perigenic (from the sides of the 

 parietal coenenchyma), or calycular, arising inside the 

 cup of the parent. 



There are two sub-classes: i. Zoantharia (Hex- 

 actinia' having the mesenteries and simple, rarely 

 branched tentacles, in multiples of six (or five) ; the 

 former are in pairs ; some or all of them bear longitu- 

 dinal muscular bands (vanes) ; around the mouth is 

 often an annular canal communicating with the several 

 perivisceral spaces ; they are marine, and have no 

 central horny axis in their ccenenchyma, except in 

 Antipathidae. 



Three orders are included: i. Malacodermata 



sea anemones ; rarely colonial, with either no corallum 



or a f<-w spicules ; the body cavity is distended by 



, which can be expelled on irritation, causing 



a rapid collapse ; the tentacles are numerous, the 



: arate (except Sagartia troglodytes), the body 



cylindrical, and the craspeda developed. They can be 



multiplied by artificial division; the embryos are 



plunuliform, then become ovate, and settling down 



sometimes in eight days), a mouth forms at the larger 



end ; the wall of the digestive sac forms as a ring 



around the mouth, which throws down into the body 



cavity.* At first the tentacles are live or six, and the 



many, but they increase in number 



rapidly. They ii\e t,,r several One kept by 



// for six years produced 276 young. In the 



D imagination. 

 I 



