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THE BORING HABITS, ETC., OF THE PHOLAS. 
W. HARRISON HUTTON, 
Leeds 
On July 18th, 1907, assisted by Mr. Talbot Thompson of 
Scarbro’, I collected a number of Pholas dactylus and P. candida 
on the rocks in the North Bay, Scarbro’. These I brought 
home and placed in my marine aquarium on the rgth. 
Most of them were in their bores in the pieces of rock we 
had broken from the scars, but a few were loose. As all the 
Pholas were found in a very soft blue rock (Oxford Clay), I 
placed some fairly soft pieces of the rock on the bottom of 
my aquarium; upon these I placed the Pholas that were 
loose, or had no bores, and although they were upon and 
amongst the pieces of soft rock six days, they made no 
attempt to bore into them, that I could detect, though I 
examined the pieces very carefully. I then removed two, 
and placed them in small holes that I had made in a piece 
of the rock; these holes accommodated about three parts 
of the shells. Four days later I found these were slightly 
enlarged, and, in a further four days, the shells were com- 
pletely embedded in the rock. Another specimen that had 
bored through the piece of rock, and had fallen out of the 
other side, I replaced, and each time it worked its way out of 
the other end. Then I placed it upon a piece of soft rough 
rock; but for three days it made no attempt to bore amongst 
the inequalities of the rock. 
From the preceding it seemed clear that the Pholas do 
not ‘ bore’ into the rocks, but the young fry are deposited 
or find their way into the very small holes and inequalities of 
the clays and rocks, and, lodging in them, gradually enlarge 
the holes, as they grow, by a slow continual rotatory movement. 
As they grow larger the aperture grows with them, and if they 
are at any time removed after they have acquired some growth, 
they cannot make themselves a new habitation. 
I repeated the experiments the year following with the 
same results. 
I was surprised at the length to which the Pholas was able 
to extend its syphon ; one specimen (and in proportion all the 
specimens were similar), measured just over 1} inches, when 
within its shell; but when it extended its syphon it measured 
34 inches. 
This year I had an interesting experience when collecting 
Pholas in the North Bay, Scarbro’. I broke away the rock 
so that the mollusca would fall out. I then waited until the 
water in the pool, into which they had fallen, cleared, so that 
I could pick them out. To my surprise, however, I could not 
find a single specimen. This occurred two or three times in 
1911 Dec. I. 
