ON ACEPHALA. 385 
pretty nearly inexplicable, although, in a certain degree, the 
first may be referred to the figure of the determining body, 
the second and third to the vigour and duration of life in the 
animal. M. de Blainville says on this subject, 
“ T have attempted several times, in the small pearls which 
merchants name seed-pearls, to find this little kernel in their 
interior, in which I succeeded, though the trial took several 
days, and I was obliged to employ an acid much stronger 
than the acetic, namely the sulphuric acid. I can even say 
that it cost mea good deal of trouble, so that we may entertain 
some doubts respecting the celebrated anecdote of Cleopatra, 
who, with the intent of expending a sum much greater than 
Antony had done in his most sumptuous repasts, where he 
had lavished the riches, and exhausted the Juxuries of the 
East, took a pearl from her ear, of considerable bulk and 
value, put it into vinegar, where it was supposed to be dis- 
solved, and swallowed it. To effect such a purpose, vinegar 
must be very strong, and many weeks, perhaps months, 
would be necessary to complete the dissolution. Some of 
these small pearls, in which, nevertheless, I could trace no 
pedicles of attachment, were equally formed of layers, al- 
though often not exactly concentric, but without any interior 
kernel; so that we must necessarily admit a third genus of 
pearls, which is formed independently of the shell, indepen- 
dently of a foreign body, and which would be but a sort of 
extravasation of the shelly matter, without doubt, in the 
mantle, perhaps even in its edge, that is to say, in the part 
which forms the greatest quantity of calcareous matter. The 
origin of this, however, may be in some accidental or external 
irritation produced on the edge of the mantle, or, in fine, in 
some internal malady of the animal, and in that case, it would 
be nearly impossible to determine the formation of these 
pearls. It is not so with the first two genera. We know, in 
fact, that certain shells may be brought to produce pearls by 
VOL. Xt. ce 
