CORAL BUILDERS. 



225 



being narrowed like the upper, expands into a 

 funnel-shaped mouth in which the chamber wall is 

 folded inwards. From this point the structure 

 becomes a slender cord, which, pass- 

 ing back to the upper end of the 

 capsule, winds loosely round and 

 round the chamber, at first regularly, 

 but afterwards in a more intricate 

 manner, until it fills the lower portion 

 of the cavity. Under pressure, or 

 at the will of the animal, the fusi- 

 form chamber and its twining thread 

 are shot forth with inconceivable ra- 

 pidity. When fully expelled the 

 thread is often twenty, thirty, or even 

 forty times the length of the lasso- 

 cell, though in some species it is 

 much shorter. It may be added that 

 the basal portion of the thread (lasso) 

 is often ornamented by a thickened 

 spiral band, in which are inserted a 

 series of firm tapering bristles (fig. 

 46). 



" It has long been known," says 

 Gosse, "that a very slight contact 

 with the tentacles of a polype is 

 sufficient to produce, in any minute animal so 

 touched, torpor and speedy death. Since the dis- 



Q 



FIG. 46. 



BASAL PORTION 

 OF LASSO. 



