Mr GuUand on the Sense of Touch in Astacus. 163 



stouter than on any other part of the body ; in the 2d maxilla 

 they are longer, and approach more nearly to the ordinary 

 type. The setse on the palps, between the lacinise and round 

 the edges of the scaphognathite, are fringing setpe, which 

 show various modifications. 



If the three pairs of appendages just spoken of be examined 

 in situ, it will be noticed that the tactile setse here, as on all 

 other parts of the animal, are only present on external sur- 

 faces, where they can be of use. From the position of these 

 appendages it is impossible to get at them for experimental 

 purposes in the uninjured animal, or without touching other 

 sensitive parts. 



\st Maxillipede (1st thoracic appendage). — The tactile setse 

 are ranged along the inner edge of the lacinia interna (coxo- 

 podite) and the lacinia media (basipodite), in the latter alone, 

 in the former with a considerable admixture of fringing setse. 

 On the rest of the endopodite and the exopodite there are 

 only fringing setse. 



2d Maxillipede (2d thoracic appendage). — The arrangement 

 of the tactile setse is very similar to that on the 3d maxilli- 

 pede, while on the 1st it closely resembles that of the maxillse. 

 The tactile setse are numerous, and are mainly found in the 

 fringe that runs along the inner edge of the endopodite. 

 Here they are long, strong, and thickly set, and stand in 

 several rows. On the basipodite and ischiopodite there are 

 no fringing setse, but on the meropodite and succeeding seg- 

 ments there are some curiously modified fringing setse, very 

 similar to those which M'Intosh describes as occurring on 

 the maxillipedes of Carcinus mcenas, whose secondary bristles 

 are short, thick, and elliptical in form, and are placed, not at 

 opposite edges, but both at the extremities of one surface 

 (PL VIIL, Fig. 8). On the tip of the dactylopodite are some 

 very thick and short tactile setse similar to those on the 1st 

 maxilla. A large tuft of tactile setse springs from the ex- 

 ternal edge of the propodite, but otherwise that margin is 

 free from setse. There are a few tactile setse scattered over 

 the exopodite. 



2>d Maxillipede. — The tactile setse are arranged here in 

 much the same way as in the foregoing limb. The ischio- 



