MDA-MATS AND SHELLY COEALLINES. 67 



" Broad Horn-wrack," and "Leafy Sea-mat," are the 

 names which the old collectors gave to this object; and 

 modern naturalists have given it the scientific appella- 

 tion of Flustra foUacea, and arrange it in the class 

 Polyzoa, a group of animate beings, which have much 

 of the form of Polypes, and much of the structure of 

 Mollusks. 



"W"e cut off a little piece from the end of one of the 

 lobes, and put this upon the stage of the microscope. 

 We now see that the cells are disposed in nearly par- 

 allel rows ; but so that those of one row alternate with 

 those of the next, quincunx fashion, the middle of one 

 cell being opposite the end of its right and left neigh- 

 bours ; — or like the meshes of a net. The cells extend 

 over the whole leaf, and are spread over both its sur- 

 faces in this case ; the united depth of two cells consti- 

 tuting the thickness of the leaf-like structure. There 

 are other species, more delicate, which have but a sin- 

 gle series of cells, all opening on the same side of the 

 leaf. 



Each individual cell is shaped like a child's cradle ; 

 and if you will imagine 20,000 wicker cradles stuck 

 together side by side in one plane, after the quincunx 

 pattern I have just mentioned ; and then the whole 

 broad array turned over, and 20,000 more glued on to 

 these, bottom to bottom, you will have an idea of the 

 framework of this pale-brown leaf; — dimensions, of 

 course, being out of the consideration. The number 

 may appear somewhat immense, yet it is no larger than 

 the ordinary average, as I will soon show you. I meas- 

 ure off a square half-inch of this leaf, which I carefully 

 cut out with scissors ; now with the micrometer count 

 the cells in the square piece. — ^You find 60 longitudinal 



