HETEROMORPHOSIS 153 
or the foot of Cerianthus is amputated, or if a piece is cut 
out of a Cerianthus, the fragment, if not too small, and if 
external conditions permit of it, again assumes a vertical 
position, with its oral end directed upward and its aboral 
end directed downward. I shall now describe these phe- 
nomena in greater detail. 
1. If a Cerianthus is laid upon the bottom of a vessel 
covered with sand, after a few minutes the foot of the ani- 
mal begins to bend downward near its tip and to bore into 
the sand. In half an hour or less (at the proper temperature 
and with irritable animals) the entire animal has buried itself 
vertically in the sand up to its head. It remains perma- 
nently in this position, if other circumstances do not induce 
it to move. 
2. A wire net, the meshes of which are so narrow that 
the body of a Cerianthus can only with difficulty be drawn 
through them, is supported horizontally upon a glass vessel 
and set into the aquarium. A Cerianthus is laid upon the 
wire net. After a few minutes the foot of the animal begins 
to turn downward, and to bore through one of the meshes of 
the wire net. That portion of the foot which has passed 
through the wire net assumes an absolutely or nearly ver- 
tical position, and remains so permanently. No change 
occurs at the oral pole, except that the tentacles close together 
so that they look like a brush, the handle of which is formed 
by the remaining portion of the animal. The animal crowds 
its body more and more through the mesh in the net, until 
it finally attains the vertical position shown in Fig. 26. 
3. This orientation can also be reached within half an hour. 
But while the Actinian generally remains in the sand after 
having buried itself vertically in it, an animal upon the wire 
screen rarely retains the orientation described longer than two 
days; it either works itself entirely through the wire screen, 
or else retracts its foot to bore it through another mesh 
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