880 ANATOMY AND DEVELOPMENT 



be shewn in the systematic part of this memoir 1 , forms a good 

 specific character. In Peripatns capensis (PI. 48, 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. 

 49, fig. 1 1). Posteriorly, however, the behaviour of the two blades 

 is very different. The epithelial ridge bearing "the outer blade 

 is continued back for a short distance behind the blade, but 

 the cuticle covering it becomes very thin, and it forms a 

 simple epithelial ridge placed parallel to the inner blade. The 

 cuticle covering the epithelial ridge of the inner blade is, on the 

 contrary, prolonged behind the blade itself as a thick rod, which, 

 penetrating backwards along a deep pocket of the buccal epithe- 

 lium, behind the main part of the buccal cavity for the whole 

 length of the pharynx, forms a very powerful lever, on which 

 a great part of the muscles connected with the jaws find their 

 insertion. The relations of the epithelial pocket bearing this 

 lever are somewhat peculiar. 



The part of the epithelial ridge bearing the proximal part of 

 this lever is bounded on both its outer and inner aspect by a deep 

 groove. The wall of the outer groove is formed by the epithe- 

 lial ridge of the outer blade, and that of the inner by a special 

 epithelial ridge at the side of the tongue. Close to the hinder 

 border of the buccal cavity (as shewn in PI. 49, fig. 12, on the 

 right hand side), the outer walls of these two grooves meet over 

 the lever, so as completely to enclose it in an epithelial tube, 

 and almost immediately behind this point the epithelial tube is 

 detached from the oral epithelium, and appears in section as 

 a tube with a chitinous rod in its interior, lying freely in the 

 body-cavity (shewn in PI. 49, figs. 13 16 /?). This apparent 

 tube is the section of the deep pit already spoken of. It may 



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

 separately- 



