ANATOMY AND DEVELOPMENT OP PERIPATUS OAPENSIS. 241 



specimens to make out the exact distributions of the tracheal 

 apertures, but I have been able to make out certain points 

 about them. 



There is a double row of apertures on each side of the 

 median dorsal line, forming two sub-dorsal rows of apertures. 

 The apertures are considerably more numerous than the legs. 

 There is also a double row of openings, again more numerous 

 than the legs, on each side of the median ventral line between 

 the insertions of the legs. Moseley speaks of a median row in 

 this position. I think this must be a mistake. 



Posteriorly the two inner rows approach very close to each 

 other in the median ventral line, but I have never seen 

 them in my section opening quite in the middle line. Both 

 the dorsal and ventral rows are very irregular. 



I have not found openings on the ventral or dorsal side of 

 the feet but there are openings at the anterior and posterior 

 aspects of the feet. There are, moreover, a considerable 

 number of openings around the base of the feet. 



The dorsal rows of tracheal apertures are continued into the 

 head and give rise in this situation to enormous bundles of 

 tracheae. 



In front of the mouth there is a very large median ventral 

 tracheal pit, which gives off tracheae to the ventral part of the 

 nervous system, and still more in front a large number of 

 such pits close together. The tracheae to the central nervous 

 system in many instances enter the nervous system bound up 

 in the same sheath as the nerves. 



The Muscular System. 



The general muscular system consists of — (1) the general 

 wall of the body ; (2) the muscles connected with the mouth, 

 ])harynx, and jaws; (3) the muscles of the feet; (4) the 

 muscles of the alimentary tract. 



The muscular wall of the body is formed of — (1) an external 

 layer of circular fibres ; (2) an internal layer of longitudinal 

 muscles ; (3) a layer of transverse fibres. 



