222 PEOFESSOR r. m. balfoue. 



the radial fibres of the pliarynx. The muscular fibres just 

 described are clearly adapted to give a sawing motion to the 

 tongue, whose movements may thus, to a certain extent, be 

 compared to those of the odontophor of a mollusc. 



In addition to the above set of muscles, there are also trans- 

 verse muscles, forming laminae between the fibres just described. 

 They pass from side to side across the tongue, and their action 

 is clearly to narrow it, and so cause it to project outwards from 

 the buccal cavity. 



On each side of the tongue are placed the jaws, which are, 

 no doubt, a pair of appendages, modified in the characteristic 

 arthropodan manner, to subserve mastication. Their structure 

 has never been satisfactorily described, and is very complicated. 

 They are essentially short papillae, moved by an elaborate and 

 powerful system of muscles, which are armed at their free ex- 

 tremities by a pair of cutting blades or claws. The latter struc- 

 tures are, in all essential points, similar to the claws borne by 

 the feet, and, like these, are formed as thickenings of the 

 cuticle. They have therefore essentially the characters of the 

 claws and jaws of the Arthropoda, and are wholly dissimilar 

 to the setse of Chaetopoda. The claws are sickle-shaped and, 

 as shown in PI. XIV, fig. 5, have their convex edge directed 

 nearly straight forwards, and their concave or cutting edge 

 pointed backwards. Their form differs somewhat in the different 

 species, and, as will be shown in the systematic part of this 

 memoir,^ forms a good specific character. In Peripatus ca- 

 pensis (PL XV, fig. 10) the cutting surface of the outer blade 

 is smooth and without teeth, while that of the inner blade 

 (fig. 9), which is the larger of the two, is provided with five or 

 six small teeth, in addition to the main point. A more important 

 difference between the two blades than that in the character 

 of the cutting edge just spoken of, is to be found in their relation 

 to the muscles which move them. The anterior parts of both 

 blades are placed on two epithelial ridges, which are moved by 

 muscles common to both blades (PI. XVI, fig. 11). Posteriorly, 



^ Some material for this memoir was left by Prof. Balfour, which will be 

 published separately. 



