166 STUDIES IN GENERAL PHYSIOLOGY 
tube, the former constructs a firm tube of mucus in the 
course of a few hours, while the latter which is kept in a 
test-tube, and the skin of which encounters but little friction 
from the smooth glass, forms a scarcely perceptible veil in 
the course of twenty-four hours. The greater amount of 
friction brings about a greater secretion and a more exten- 
sive tube-building. 
3. I fastened a Cerianthus to the underside of a cork 
floating at the surface of the aquarium. The Cerianthus 
was fastened to the cork by passing a pin through its body. 
The head and foot of the animal hung down loosely upon 
either side of the pin. I waited four weeks, but no mem- 
brane was formed upon the parts which did not come in con- 
tact with solid bodies. But a secretion occurred at those 
places where the Cerianthus rubbed against the cork or the 
head of the pin. The mass of mucus secreted at these points 
attained the thickness of a finger in four weeks. 
The wound occasioned by the pin was not the cause of 
this secretion, but only the friction, for I observed the same 
phenomena in uninjured Cerianthi which remained for some 
time in the meshes of a wire screen. Only in the latter case 
it is very difficult to keep a Cerianthus very long in this 
position without movement. 
The formation of a tube by Cerianthus offers therefore 
the same evidence of “artistic impulse” as the secretion of 
saliva during mastication. 
XV. EXPERIMENTS ON ORGANIZATION AND IRRITABILITY IN 
SOME OTHER ACTINIA 
1. I have made experiments similar to those upon Ceri- 
anthus on the determination of the situation of the new head 
in a number of other Actinians— Actinia equina of the Bay 
of Naples and the East Sea, Actinia cari, Adamsia Rondel- 
letti, Anemonia sulcata, Cereactis aurantiaca, etc. 
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