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v \ 
-EXXIII. A Letter from Dr. Parfons, F.R.S . 
to Mr. Peter Collinfon, F. R . S. concern- 
ing the Shells of Crabs . 
Dear Sir, Red-lion Square, April 22, 175Z, 
Read April 30, X T THEN I had examined the crabs, 
Vv fent you by Mr. Cook, I con- 
fds’d I had fome doubts concerning them, which at 
prefent are clear’d up, by the lad: view I took of 
them. However, as I made no manner of question 
of the animal’s calling his Ihell at certain feafons, 
your friend needed not be at the pains to quote fo 
many authors, to prove what every naturalift knew 
before. I only wanted to be fatisfied, that the old 
exuvid were thofe of the loft crab ; which the muti- 
lated claw has indeed given me alfurance of, how- 
ever difficult it may be to conceive the manner of his 
quitting it. 
It is no doubt a curious fpecimen, and, I hope, 
will be very convincing to your correfpondent abroad, 
in fupport of a fad, which nobody, who has any 
pretence to natural knowlege among us, would heli- 
tate about 5 any more than we do of that animal’s 
fhaking off one or more limbs occalionally for his 
prefervation. Nor is the manner of his acquiring a 
new limb in any wife different from that of his ob- 
taining a fucceeding new fhell ; which is from a la- 
tent organization of the part ready for being indurated 
in due time, after the difcbarge of the old one ; at 
which time, and not before, the telfaceous matter has 
room for its fecretion thro’ its proper emundories. 
This 
