122 SUPPLEMENT 



tubercle; doubtless the rudiment of an appendage, but in 

 which no setse 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 ]3igmentum 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 



