124 SUPPLEMENT 



1. 



proximatecl in consequence of the absence of the viscera, pro- 

 ceed li'om a central point, and form radii at the circumference 

 of the discus, which we have said terminates the body of the 

 leech, while the circular fibres preserve their usual disposition. 



The apparatus of digestion is pretty similar to that of most 

 of the class : there is no evident serous lacuna between the 

 exterior and that which constitutes the intestinal canal ; on 

 the contrary, these two parts are united by numerous cellular 

 and vascular bridles, which pass from one to the other, and 

 thus produce a sort of strangulations, and then a series of 

 pouches or dilatations of the intestine. 



We have already remarked, that the anterior extremity of 

 the leeches presents an aperture more or less considerable, 

 conducting into a cavity sometimes conformed like a cupper ; 

 at the bottom of this cavity exists a labial fold, composed of 

 three lobes, not very distinct, rather nan-ow, two lateral and 

 one ventral, leaving between them a triangular space, the sum- 

 mit of which is upwards. In this space appear projecting 

 more or less the dentiferous tubercles; these tubercles are the 

 same in number as the labial folds, but in an inverse order. 

 Their form is sublenticular. They are placed on a level, so 

 that the free part of their edge, very obtuse, converges towards 

 the longitudinal axis of the body, and the adherent part is 

 confounded with the contractile stratum of the external en- 

 velope. They are of a yellowish and shining white, and 

 appear to be of a denser tissue and more compact than the rest 

 of the contractile stratum of which they are a dependence. 

 They seem entirely contractile, though there is at their dorsal 

 base a muscular fasciculus, more! distinct, forming a part of 

 the longitudinal stratum, extending under the oesophagus, and, 

 besides, another transverse bridle, very visible, particularly 

 between the two inferior tubercles. It is on the very blunt 

 edge, however, that one can distinguish, by the assistance of a 

 glass of very short focus, a double series of corneous teeth, ex- 



