HETEROMORPHOSIS 165 
smooth coating. If the Cerianthus is pulled out of the sand, 
it is found to be incased in a soft tube which is smooth 
internally and covered on the outside with fine grains of 
sand. The animal can be drawn out of the tube without 
injury. Itseemsvery human that the animal should arrange 
itself comfortably in the sand and protect itself against 
unwelcome visitors by building a tube about itself. This 
formation of tubes by Cerianthus appears to belong to those 
cases to which the old phrases of ‘“‘instinct” and “artistic 
impulse of animals” might be applied. It may perhaps be 
of interest to some of the readers to become acquainted with 
the following simple experiments which show upon what 
foundation anthropomorphic conceptions of life-phenomena 
are occasionally based. 
1. If a Cerianthus is carefully drawn out of its tube and 
laid upon a very thin layer of sand in which it cannot burrow, 
a secretion is soon formed at the surface of those portions of 
the body which rub against the sand. The surrounding 
particles of sand stick to this secretion. The continued 
movement of the animal, and the propagation of stimuli from 
those parts of the animal which are rubbed in the sand to 
neighboring parts of its surface, cause the secretion to be 
poured out over the entire surface of the body of the animal. 
The tube is then completed. It is at first very thin, but 
becomes thicker in the course of time, as more secretion is 
poured out in consequence of the continued friction. 
According to these observations, therefore, the entire process 
of ‘“‘tube-building”’ is nothing but a process of secretion, the 
stimulus for which is found in the friction of the surface of 
the body against solids. This is confirmed by the following 
experiments. 
2. The thickness of the tube is dependent upon the 
degree of friction. If one Cerianthus is laid upon sand, 
while another is introduced into a carefully cleaned test- 
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