364 THE BIRD'S-IIEAD CORALLINE. 



decomposing animal substance in water invariably attracts crowds of infusory animalcules, 

 which then breed with amazing rapidity, so as to form a cloud of living atoms around the 

 decaying body, quite invisible in the aggregate to the unassisted eye ; and these remain in the 

 vicinity, playing round and round until the organic matter is quite consumed. Now, a tiny 

 annelid or other animal caught by the bird's head of a polyzoon and tightly held, would 

 presently die; and though in its own substance it would not yield any nutriment to the 

 rapturer, yet by becoming the centre of a crowd of busy infusoria, multitudes of which would 

 constantly be drawn into the tentaculean vortex and swallowed, it would be ancillary to its 

 support, and the organ in question would thus play no unimportant part in the economy of 

 (he animal." 



We now proceed to the vibraculum. It is hollow, the interior being tilled, during the life 

 of the animal, by a fibrous contractile substance, which enables the organ to perform its 

 curious movements. These movements are very irregular as regards time, but very regular in 

 their directions, each vibraculum sweeping slowly over the whole surface within its reach, first 

 moving in one direction and then in the other, and it is sufficiently notable that these move- 

 ments will continue for several days after the death of the polype to which it is attached. 



The mouth of a cell belonging to another polyzoon shows a curious operculum, with a 

 branched form, like the horn of a fallow deer, and may be contrasted with the simple spiny 

 operculum. 



I am now going to describe several curious and bizarre forms of Marine Polyzoa. One of 

 them is the Bull's-horn Coralline of Ellis — the Ladies' Slipper, as it is more elegantly and 

 equally appropriately named at the present day. The cells of litis species bear a considerable 

 resemblance to a series of delicate, slender-toed slippers, adherent to each other, while from 

 the opening protrudes the beautiful bell-shaped circle of tentacles. Sometimes a rudimentary 

 cell may be found, but always below the aperture. 



A common creature is the Snake-head Coralline, so called from the extraordinary simili- 

 tude with a reptile. 



In another species, which is called Bednia mirdbilis, the mouth is surrounded with a 

 series of thorns or spines. It is found mostly on shells. Each cell is united to its pre- 

 decessor and successor by a slender tube. 



The curious Farciminaria, remarkable for the array of short and stout spines with which 

 its surface is thickly studded, is a New Zealand species, and appears to be the sole representa- 

 tive of its family. It grows in slender branches, which are dichotomous. 



In the family to which the Gemelldria loriedta belongs, the cells are arranged in pairs and 

 opposite each other, the orifices of the pairs looking in the same direction. This species is the 

 Coat-of-Mail Coralline of Ellis, deriving ils name from the shape of the cells, which bear no 

 slight resemblance to steel corslets. 



The succeeding family, of which the Dimetopia spiedta is an example, may be known by 

 the arrangement of the cells, which are in pairs, but with their mouths placed at right angles 

 to each other. When growing, it is a very pretty species, being white, nearly transparent, 

 and attaining a height of about three inches. It grows in thick tufts, and is found in Bass's 

 Straits. 



The Shepherd' s-pnrse Coralline of Ellis {Notdmia bursdria) is a common European 

 species, and its peculiar avicularium shows a tobacco-pipe-like head. 



A most curious vibraculum, which is toothed like a saw, belongs to a creatine called 

 Caberta palagom'ca, living in the country from which it takes its specific name. 



On a very remarkable species, the Bicelldria cilidta, the cells are surrounded by long 

 processes. An avicularium belonging to another species of the same genus is conspicuous for 

 the enormously long stalk of the head, and the three finder-like appendages at the base. 



A tolerably common European species is the Bird's-head Coralline (Bugula avicularia), 

 popularly so called on account of the number, shape, and activity of the avicularia. Our 

 attention is now called to a well-known polyzoa, which may be found lining the sides of rock- 

 pools, or affixed to shells, and even to living crustaceans, the spider-crab being often enveloped 



