CORALS AND CORAL MAKERS. 13 



m.irgins of the mouth over the mollnsk or crab, until the 

 ^' .:oIe is inclosed and passed into the digestive sac ; and when 

 tl, estion is complete, the shell and any other refuse matters 

 are easily got rid of by reversing the process. 



But the Actinia owes nearly all its power of attack to its 

 concealed weapons, which are carried by myriads. These are 

 what Agassiz has called lasso-cells^ because the little cell-shaped 

 sheath contains a very long slender tubular thread coiled up, 

 which can be darted out instantly when needed. As first 

 observed by Agassiz, the tubular lasso escapes from the cell by 

 turning itself inside out, the extremity showing itself last, and 

 this is usually done " with lightning-like rapidity." Then 

 follows the poison. The lasso-cells (called often nettling cells, 

 and by Gosse cnidcs, and thi-ead capsules) are usually less 

 than a 200th of an inch in length ; but they are thickly crowded 

 in the larger part of the skin or walls of the tentacles, and 

 about the mouth ; also in the walls of the stomach, and 

 within the visceral cavity in white cords hanging in folds from 

 the edge of the septa. Thus the polyp is armed inside and 

 out. The mollusk or crab that has the ill luck to fall, or be 

 thrown by the waves, on the surface of the pretty flower is at 

 once pierced and poisoned by the minute lassos, and is ren- 

 dered incapable of resistance. 



The following figures, by Dr. Karl Mobius, of Hamburg, 

 illustrate admirably these organs. The views are magnified 

 700 diameters. Figure i represents one of the lasso-cells of 

 the Actinia, Corynactis viridis^ with its lasso coiled up within ; 

 its actual length is about a 350th of an inch. Figure 2 is the 

 same with the lasso out, though less than half of the long 

 thread is shown. Figure 3 is the lasso-cell of the polyps of a 

 European coral, the Caryophyllia Smithii. It differs from 

 figure I in having the basal part of the lasso within the cell or 

 sheath strait and stout ; it is this part which makes the first 

 portion of the extended lasso. A view of part of the latter is 

 represented in figure 4, and of the extremity of the same in 

 figure 5. The lasso-cells in the above species are from a 240th 

 to a 360th of an inch in length. In the Aletridmm viargina- 



