Manchester Memoirs, Vol. L (1905), No. \. 3 



large ones opening into the buccal cavity just behind and 

 close to the base of the inner jaw on each side, and 

 running backwards for some distance, at first just outside 

 the lateral nerve cords (yfig. 5, B. ir.) and then above and 

 just inside the salivary glands. These buccal tracheal 

 pits have a thick chitinous lining, and may be traced back 

 in a series of transverse sections very nearly to the level 

 of the second pair of legs. They give off along their 

 course and from their extremities an immense number of 

 very fine tracheal tubes. When the jaws are removed, 

 these enormously elongated tracheal pits may be pulled 

 out in connection with them, and the chitinous lining of 

 the pit appears to pass over into the chitinous covering of 

 the smallest accessory tooth of the inner jaw." 



On comparing these two accounts it is quite evident 

 that they are descriptions of similar structures ; but there 

 is a striking difference in the characters and functions 

 ascribed to them. In Balfour's account there is a solid 

 chitinous jaw-lever in an epithelial pocket, to which are 

 attached " a great part of the muscles connected with the 

 jaws ;" whereas Dendy describes them as buccal tracheal 

 pits having a chitinous lining and giving off "along their 

 course and from their extremities an immense number of 

 very fine tracheal tubes." On the other hand their figures 

 are very similar. 



In working over series of sections of P. balfouri and 

 P. novae zealandiae I suspected that Prof Dendy had 

 mistaken the striated muscle fibres which move the jaw- 

 levers for tracheal tubes and "enormously elongated tracheal 

 pits." I called his attention to this ; and he kindly sent 

 me his sections of Ooperipatus oviparus (from which his 

 description and figures had been made). An examination 

 of these convinced me that this was the case, and that 

 the supposed tracheal structures were muscles in 0. oviparus 



