4 Hewitt, Note on the Buccal Pits of Peripatus. 



as Balfour had described them in P. capoisis, and as I had 

 found them to be in P. balfonri and P. novae zealandiae. 



The muscle fibres which work the jaw-levers are 

 transversely striated, being the only transversely striated 

 muscle fibres which occur in Peripatus. The fine tracheae 

 are also striated, but on comparison it is found that the 

 striations of the tracheae differ considerably from those 

 of the muscle fibres. As Moseley showed (2) in the 

 first account which was given of the tracheae of Peripatus, 

 the tracheae are provided with a spiral thread, the indi- 

 vidual coils of which are fairly wide apart. Their walls 

 are extremely thin, and hard to detect, except with a high 

 power. The muscle fibres have a more dense appearance 

 than the trachea ; this is due to the fact that the striations 

 of the muscle fibres are very fine and close together, and 

 stain very readily. 



I was unable to find in any of the sections examined 

 any apertures in the epithelial pockets into which the 

 chitinous jaw-levers fit, which might serve as means of 

 communication between the buccal pits and any tracheal 

 structures, supposing the latter existed in this region. 

 Certainly no tracheal pits were given off from these 

 epithelial pockets. 



In the species examined the characters of these 

 structures are very similar, the only difference being in 

 the form of the jaw-lever, which in P. balfonri differs 

 slightly from those of /^. novae zealandiae and O. oviparns. 

 As Balfour shows, the cuticle covering the epithelial ridge 

 of the inner blade is prolonged backwards as a thick, 

 flat, chitinous rod. In the anterior region of this rod 

 the outer walls of the two grooves described by him meet 

 at the hinder end of the buccal cavity. These grooves 

 are lined by a thin cuticle, and when the fusion of the 

 outer walls of the grooves takes place, the cuticle also 



