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tubercle; doubtless the rudiment of an appendage, but in 
which no setae are perceptible. M. de Blainville appears to 
be the only author who has noticed this. 
The envelope of the leeches is soft in all its parts, and in 
all directions, so that the animal can easily pass from a semi- 
globular to a sub-linear form. The skin, properly so called, 
is adherent in all its points, and even almost confounded with 
the subjacent contractile tissue. An epidermis may be there 
distinguished, or rather a sort of varnish extremely thin, ap- 
plied on a pigmentum tolerably thick, granular, and coloured 
in various ways. The dermis itself is not very thick, it is ad- 
herent, and subtuberculous, in consequence of the great 
number of crypta with which it is sown, which give it a porous 
aspect. Each ring separated from the others by a tolerably 
deep furrow, is itself divided into two by a transverse fold, 
on which there are numerous longitudinal fissures. 
The crypta of the skin are larger, and more developed on 
each side of the belly, at every fifth ring, and form a pretty 
considerable projection or tubercle, pierced with a large pore. 
These organs, M. Thomas considered as sorts of lungs, but 
with small reason, as they never contain any air, and are 
filled with the same sort of mucosity as the other crypta of 
the skin, nor is there any thing in their position analogous to 
that of respiratory organs. Neither have they any real re- 
lation to the male organ of generation, as was supposed by 
M. Spix. 
This very soft and contractile skin of the leeches, is, in all 
probability, the only organ of sense which can be recognized 
in them. There seems to be no appendage, no cavity, which 
can be regarded as the seat of smell. There certainly may 
exist an organ of taste, probably in the sort of lips which 
precede the dentiferous tubercles ; but of this we can be by no 
means certain. 
We remark, as we have already mentioned, at the upper 
