26 CORALS AND CORAL ISLANDS. 
a kind of case or jacket, into which the upper extremity, 
which is soft and delicate in texture, may be retracted. The 
thickening of the epidermis in this middle portion is produced 
through the entangling of disintegrated cells and minute for. 

1. PEACHIA HASTATA, G.; 2. EDWARDSIA CALLIMORPHA, G.; 3. HALOCAMPA 
CHRYSANTHELLUM, G. 
eign particles, sometimes in part spores of Confervx, by 
means of the mucus of the surtace; and if the layer is re- 
moved, as it may be, the skin will again become covered. 
This species, like others of the genus, lives buried to its neck 
in the sand, that is, with the soft upper extremity protrud- 
ing If disturbed, the head is suddenly drawn in, together 
with more or less of the following jacketed part of the body. 
The warty prominences on some warty species have the 
power of clinging by suction to a surface, and such Actiniz 
often cover their sides thus with bits of shell or of other sub- 
stances at hand. Where there are no warts the contracted 
