12 A Guide to the Zoological Collections in the 



METAZOA CCELENTERATA. 



[Case® 1—8 along the SS^stcrn sil)c, anb 9—16 along the 

 ©astern ©ibc of the Olatlerj)]. 



The Coelenterata, or Zoophytes, are multicellular ani- 

 mals, most of which are immovably fixed and have the 

 power of increasing either by fission, or by budding like 

 plants, to form tree-like colonies. 



Many of them were formerly classed with plants, and 

 their name of Zoophyte, or "Plant animal", indicates this 

 superficial resemblance. 



The group includes the Sponges, the Sea-firs and Sea- 

 jellies, the Sea-pens, the Corals, and the Sea-anemones. 



In the Ccelenterata-iy^e the division of labour has pro- 

 gressed to the extent of segregating the cells of which the 

 body is made up into two layers — an outer chiefly defen- 

 sive layer known as the ectoderm, and an inner chiefly 

 digestive layer known as the endoderm. Between these 

 two layers a middle chiefly supporting layer, known as the 

 mesoderm, is afterwards developed. 



The Coelenterata are divided into two great groups — 

 (i) the /'^'^{/6'rrt:. or Sponges, which have inhalant pores in 

 the body-wall, but have no mouth, no tentacles, and no 

 stinging cells ; and (2) the Ctiidaria, or Stinging Zoo- 

 phytes, which have no inhalant pores in the body-wall, but 

 have a mouth, tentacles, and stinging cells. 



PHYLUM I OF THE CCELENTERATA. 



PORIFERA (SPONGES). 



[(Eases 1—3 along the SEestern sik of the (lallevj)]. 

 The typical form of the simple sponge-animal is that of 

 a tube closed and fixed at one end and free and open at 



