44 8 SEA MATS, OR HORNWRACKS. 



The succeeding family, of which the Dimetbpia spicdta, fig. G, 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. 



Fig. H represents the Shepherd's-purse Coralline of Ellis, Notamia bursdria, a common 

 British species, and at I is shown its peculiar avicularium, with its tobacco-pipe-like 

 head. Several smaller birds' heads are to be seen on the main figure. 



Fig. K is given in order to show a most curious vibraculum, which is toothed like a 

 saw, and belongs to a creature called Caberea Patagonica, living in the country from 

 which it takes its specific name. 



A very remarkable species, Bicelldria cilidta, is given at fig. L, in order to exhibit 

 its general aspect, and the manner in which the cells are surrounded by long processes. 

 At fig. M is shown a greatly magnified figure of the avicularium belonging to another 

 species of the same genus, conspicuous for the enormously long stalk of the head, and 

 the three finger-like appendages at the base. 



The three remaining figures represent a tolerably common British species, popularly 

 called the Bird's-head Coralline (Bugula avicularia), on account of the number, shape, 

 and activity of the avicularia. Fig. O shows the natural size of the 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 in its soft plumy branches to such an extent that 

 it marches beneath their shade, like Macduff's army under its leafy disguise. At N is 

 seen a magnified portion of the same species, with the avicularia in various attitudes, 

 one being shown in the act of intercepting a minute worm that has happened to cross 

 its sphere of action ; and at P is seen one of the bird's heads greatly magnified, so as 

 to show its wonderful resemblance to the object whence it derives its name. I know 

 scarcely a more wonderful sight than is presented by a living specimen of the Bugula, 

 with its wonderful appendages in full action. As if moved by machinery, they nod up 

 and down like automata, sometimes throwing themselves back like the head of a fantail 

 pigeon ; the mouth opens slowly, with a wearied kind of air, that almost forces the ob- 

 server to yawn in sympathy with the deliberate movement, while ever and anon the 

 jaw suddenly closes with a snap so sharp that the ear instinctively watches for the 

 sound. 



EVERY one who has walked along the seashore must have observed the pretty leaf- 

 like Sea Mats strewn on the beach, and admired the wonderful regularity of their struct- 

 ure, perceptable to the naked eye ; but when magnified even by a pocket lens, their 

 beauty increases in proportion to the power employed, and the marvellous arrangement 

 of the cells, and the orderly system in which they are placed, are almost beyond belief. 

 Beautiful, however, as they are in this state, they are but the dead and lifeless habita- 

 tions of the creatures who built the wondrous cells, and the only method of showing the 

 Sea Mat in its full glory, is to take a living specimen from the stone or shell to which 

 it is affixed, and watch it under the microscope while the creatures are still in full ac- 

 tivity. At Plate III. fig. A, is shown a portion of the common Sea Mat, sometimes 

 called the Hornwrack, of its natural size, and fig. B represents a few cells of the same 

 species rather highly magnified. 



On the upper right-hand cell may be seen the funnel-shaped group of tentacles be- 

 longing to one of the animals, and in the centre is a curiously shaped cell, which is 

 analogous to the birds' heads which we have so lately examined, the place of the lower 

 jaw being supplied by a kind of lid. 



The peculiar manner in which the polypes of the Sea Mat protrude themselves is 

 quaintly and accurately described by Mr. Gosse in his " Evenings at the Microscope." 

 After pointing out the cradle-like shape of the cells, he proceeds as follows : " Suppose 

 that a coverlid of transparent skin were stretched over each cradle from a little within 

 the margin all round, leaving a transverse opening just in the right place, viz. over the 

 pillow, and you would have exactly what exists here. There is a crescent-form slit in 



