30 CORALS AND CORAL ISLANDS. 
The Actinia appears, at first thought, to be well prepared 
for securing its prey through its numerous tentacles. But 
these are generally too short for prehension. Yet the disk often 
aids them by rolling over the captured animal, and pushing it 
down into the stomach. At the same time, the mouth and 
stomach are both very extensile, so that an Actinia may swal- 
low an animal nearly as large as itself; it gradually stretches 
the margins of the mouth over the mollusk or crab, until the 
whole is enclosed and passed into the digestive sac; and when 
digestion 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 dasso-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 it- 
self last, and this is usually done “ with lightning-like rapidi- 
ty.” Then follows the poison. The lasso-cells (called often 
nettling cells, and by Gosse cnide, and thread capsules) are 
usually less than a two-hundredth 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 
tall, 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 rendered incapable of resistance. 
The following figures, by Dr. Karl Mobius, of Hamburg, il- 
lustrate admirably these organs. The views are magnified 
