AMPHITRITE. 221 
then, as the turbid matter descends gently from above, the creature will 
forsake its concealment, display its plume, and renew its labours. 
More than mere instinct must be ascribed to all this, for the archi- 
tect can certainly testify a certain discrimination, both of what is essen- 
tial to be done, and in the mode of doing it, whether in simple prolonga- 
tion of its dwelling, or in repairing attainable breaches. Thus its revo- 
lution is either partial, complete, or repeated ; it advances and returns, 
plastering the same portion once and again ; nor is it satisfied with a 
single application of its trowels in moulding the work ; their office is 
varied and appropriately resumed. 
To obtain satisfactory exhibition of the process above detailed, a 
tall vessel, little exceeding three inches in diameter, should be employed, 
which will bring the whole within the focus of an ordinary lens ; or a 
smaller vessel may suffice, according to the specimens. The water should 
rise considerably above the object, that the muddy drops may descend 
in gentle dispersion. 
The softest earthy particles are the most congenial to the delicate 
structure of the ciliated funnel. Nevertheless grains of sand enter the 
lower part of large tubes, in the natural state, while the higher consists 
of the wonted materials. Short tubes, those under six inches, have con- 
sisted exclusively of mud and gluten. Long tubes, those of twenty or 
twenty-four inches, have consisted, first, of the finest sandy particles, for 
a third upwards, of agglutinated or silky matter; next, of mud and 
gluten as usual, for the remainder. Their foundation was never obtain- 
ed, and although some, extending two feet, seemed of this latter com- 
pound exclusively, they were also ruptured below. They appear to en- 
large gradually from a line in diameter near the foundation, to about 
three lines at the orifice. The substance of the tube is no doubt depen- 
dent on its situation. Possibly where originating near a quantity of 
sand, a portion of that ingredient becomes affixed externally with the 
glutinous secretion from the animal, while there is nothing but mud 
above to be purposely employed in the fabric. It is from the forcible 
means adopted for recovering the tubes that they are ruptured in the 
