SEA-MATS AND SHELLY CORALLINES 77 



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 im- 

 mense, yet it is no larger than the ordinary average, as 

 I will soon show you. I measure 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 rows, each containing 28 cells, 

 or thereabout. Yery well; a simple arithmetical process 

 shows that there are 1,680 cells in this square half -inch; 

 or 6,720 in a square inch. Now this very specimen, be- 

 fore I mutilated it, contained an area of about three square 

 inches; which would give 20,160 cells. This is the num- 

 ber on one surface; the other contains an equal number; 

 and thus you see that I have not exaggerated the popula- 

 tion of this tiny marine city. This, however, is by no 

 means a specimen of unusual size. 



These cells, which I compare to cradles, are of shallow 

 depth, but the head- part rises to a much greater height 

 than the foot. All round this elevated portion the margin 

 is armed with short blunt spines, two on each side, which 

 stand obliquely erect, projecting outward over the middle 

 of the next cell, which thus, in concert with the spines of 

 the cell on the opposite side, they protect. 



If you search carefully over the aggregation of cells 

 with this pocket- lens, you will perceive that on some of 

 them are seated minute white globules, which look like 

 tiny pearls. These are not placed in any regular order, 

 two being sometimes found on contiguous cells, but gen- 

 erally they are scattered at more or less remote intervals. 

 If we now apply the microscope to these appendages, each 

 globule is seen to be flat on that perpendicular side which 



