ESCHARID^. 229 



or upper surface of the dilated extremity of the polj^-cell, represented 

 at No. 2, this earthy matter is deposited in the form of minute angular 

 or rounded particles, presenting faint traces of a linear arrangement; 

 but in the main body of the polyp- cell, or the upright portion, the 

 calcareous material is arranged in beautifully regular rings, giving 

 that part of the zoophyte a peculiarly elegant appearance under the 

 microscope. This calcareous ingredient is sufficiently abundant to 

 render the contents of the radical tubes and polyp-cells indistinct; 

 and to obtain a satisfactory view of these parts it is necessary to re- 

 move the earthy matter by some weak acid. When this is done, it will 

 be found that the contents of the radical portion are coarsely granular, 

 and the wall rather thicker than those of the proper polyp-cell. The 

 latter contains an ascidian polyp, which has about twelve tentacles, 

 and no gizzard. The polyp, as far as Mr. Busk has observed, is always 

 lodged in the upright portion of the cell ; but the long retractor mus- 

 cular fibres arise near the commencement of the horizontal portion of 

 the cell, and from its upper wall, nearly at one point. 



The expanded portion of the cell, besides the special muscles of 

 the aperture, contains other muscular fibres, in all respects resembling 

 those described by Dr. Farre, as conducing to the extrusion of the 

 polyp in Bowerbanhia, and which are also very distinct in the Notomda; 

 but which, in the present instance, would seem to have for their chief 

 function the drawing-up or corrugation of the membranous portion of 

 the polyp-cell. These muscular fibres have a distinct central nucleus 

 or thicker portion, as is the case in the analogous muscles in the other 

 cases just cited." 



From the above description, the student in natural history will 

 perceive the discoveries of Mr. Busk so far differ from the accepted 

 account of this zoophyte as to remove it from the family in which it is 

 generally placed, as well as NotamAa hursmria, to the class Bryozoa. 



ESCHAEIDjE. 



This interesting family justly deserves the great attention many 

 naturalists have bestowed upon it. Linnseus named it Flusi/ra, from 

 the Saxon vtoTAflustrlcm, to weave; they are commonly called Sea- 

 mats, and resemble fine network spread over stones, rocks, shells, and 

 marine-plants. This network, when submitted to the powers of the 

 microscope, is found to be a cluster of cells, in each of which dwells an 

 animal, that protrudes its feelers when searching for food, and sinks 

 into its little home when tired, or fearful of danger. 



