SEA-ANEMONES : THEIR WEAPONS. 357 



edges curved-in, which can at pleasure be brought into 

 contact, and thus constitute a tube. Like all other internal 

 organs in these animals, its surface is richly ciliated, 

 and the ciliary currents not only hurl along whatever 

 floating atoms chance to approach the surface, but cause 

 the detached fragments themselves to wheel round and 

 round, and to swim away through the water. Though 

 there is not the slightest trace of fibre in the structure of 

 the acontium, when examined even with a power of eight 

 hundred diameters, the clear jelly, or sarcode, of which 



POETION OP ACONTIUM 



its basis is composed, is endowed with a very evident con- 

 tractility ; the filament can contract or elongate ; can 

 extend itself in a straight line, or throw its length into 

 spiral curves and contorted coils ; can bring its margins 

 together, or separate them in various degrees ; can per- 

 form the one operation at one part, and the other at 

 another, and thus can enlarge or attenuate the general' 

 diameter of the cord, apparently at will; and some of 

 these changes can be effected even in the fragment de- 



