HYDRO IDS. 



77 



long. It has the form of a polyp, with long slender tentacles ; 

 and, besides these tentacles with their lasso-cells, it has no 

 special organs except a mouth and a tubular stomach. Like 

 the fabled Hydra, if its head be cut off another will grow out ; 

 and any fragment will, in the course of a short time, become 

 a perfect Hydra, supplying head, or tail, or whatever is want- 

 ing : and hence the name given to the genus by Linnaeus. 



The Hydra is the type of a large group of species. It buds, 

 but the buds drop off soon, and hence its compound groups 

 are always small, and usually it is single. But other kinds 

 multiply by buds that are persistent, and almost indefinitely 

 so ; and they thus make mem- 

 branous coralla of considerable 

 size and often of much beauty. 



The species figured on p. 78, the 

 Hydrallmania Falcata, is one of 

 them ; in allusion to its deli- 

 cate plumes, it is called Plumu- 

 laria. Along the branches, there 

 are minute cells, each of which 

 was the seat of one of the little 

 Hydra-like animals (in this not a 

 fourth of a line long), and usually 

 with short tentacles spread out 

 star-like. Other kinds are simple 

 branching threads, and sometimes hvuka. 



the cells are goblet - shaped 



and terminal. The Tubulariae grow in tufts of thread-like 

 tubes, and have a star-shaped flower at top, often half an 

 inch in diameter, with a proboscis-like mouth at the centre. In 

 Coryne, a closely-related genus, the tentacles are shorter, and 

 somewhat scattered about the club-shaped or probosciform 

 head of the stem, so that the animal at top is far from star- 

 shaped or graceful in form ; it is in fact a very clumsy unshapen 

 thing for a Radiate. 



To the animal of the Coryne, that of the very common, and 

 often large, corals, called Millepores, is closely related, as first 



