450 



FORMS OF LEPRALIA. 



been cemented upon it. This substance is indeed closely allied to the Sea Mat, and is 

 chiefly to be distinguished by the membranous nature of the polyzoary, which will not 

 permit it to stand boldly erect after the manner of the true Sea Mat. At fig. H is 

 shown a small mass of the Membranipora pilosa, as this species is called, surrounding 

 the stem of a seaweed, and at I, a small portion of the same creature is given in order 

 to show its aspect when magnified. 



As may be seen from the illustration, the feathery plume of tentacles is extremely 

 graceful, and, when the creature is living, has a remarkably elegant effect. In a speci- 

 men now before me, viewed by a power of only thirty diameters attached to the binoc- 

 ular microscope, the polypes of the Membranipora are beautifully exhibited, some shut 

 up closely in their homes, some just putting forth their heads from the cells, others 

 half protruded, and a few with the plumy tufts displayed in all their beauty. It is as 

 well to view this and other polyzoa with different kinds of illumination, both as opaque 

 and transparent bodies, artificial light is, however, to be avoided. 



Fig. K represents a magnified portion of an allied species, Lepralia Landsborovii. In 

 the Lepralia, as well as the Membranipora, the process of development is very interest- 

 ing, especially as it can be readily watched under the microscope. 



Towards the end of May, specimens of Lepralia, Flustra, and Membranipora should 

 be procured and placed in shallow glass vessels containing sea-water. After a little 

 time, minute beings, much resembling the ordinary infusoria, are seen swimming about. 

 Presently, the " gemmules," as these creatures are technically named, become stationary, 

 affix themselves to some definite spot, and develop a feather-covered polype, being now 

 similar in shape to a single cell of the species from which it was produced. Buds, or 

 projections, are soon formed at the sides, which are rapidly developed into new cells, 

 and in their turn are the means of putting forth new cells. Thus it will be seen that 

 each polyzoary spreads from a centre ; and that, although a freegemmule is capable of 

 producing stationary cells, the greater number of cells have never passed through the 

 state of their original progenitor. When a polyzoary has attained a considerable size, 

 it is not unfrequent to find the margins of the group filled with vigorous and lively 

 polypes, being those last produced, while the centre is composed of empty cells, the 

 original inhabitants having died out from old age. 



At figs. L and M we observe two portions of Lepralia spinifera, given for the purpose 

 of showing the short sharp thorns with which the edges of the cell are guarded, and 

 the curious ovicell, notable for its beautiful sculpturing of ridges radiating around a 

 centre. Fig. N is the Lepralia trispinosa, distinguished by the three long spines from 

 which it derives its name. 



On Plate IV. in figs. A to J inclusive, are represented some of the forms assumed by 

 this large and interesting genus, which comprises between forty and fifty known species. 

 Among these especial attention must be drawn to Lepralia monoccros, or the Unicorn 

 Lepralia (fig. C), so called on account of the single horn, or club, with which it is 

 furnished ; the Lepralia a/ata, or Winged Lepralia (fig. B), remarkable for the classically 

 elegant sculpturing and the projecting " wings ; " and the Lepralia variolosa (fig. G), 

 so called on account of the peculiar mottlings which are thought to bear a resemblance 

 to the face, of a person seamed with the small pox. 



At fig. K is shown the spoor-like avicularium of the Cellepora fusca, a polyzoon notable 

 for its urn-shaped and chalky, stiff cells, arranged either irregularly or in the form 

 of a quincunx, /. e. like the cinque spots on a die, \-\ It is a native of Bass's Straits. 

 A tolerably common British species, Eschara foliacea, so called from its superficial re- 

 semblance to the scar left by a deep wound, is given at fig. L, and a very curious 

 polyzoon of the same genus, Esckara flabellaris, may be seen at fig. M, and is remark- 

 able for the hood or helmet-like ovicells. About eleven species of this genus are 

 known. 



At fig. N is shown one of the most curious of the polyzoa, named, from the external 

 resemblance which its apertures present to the meshes of a net, the Rctepora, or Net- 

 pored animal. The polyzoary of this species is hard, chalky, is only pierced on one 

 surface, and has so much the appearance of the true stony corals, that it might easily be 



