1918.] NATURAL SCIENCES OF PHILADELPHIA. 97 



transverse connectives (die) are given off to the lateral longitudinal 

 tracheae (lit, rlt). From about sections 95 to 130 the dorsal trunks 

 are almost in contact with one another and lie dorsal to the gut. 

 At about section 170 on the right, and 180 on the left, two more 

 transverse connectives (die) connect the dorsal and lateral 

 longitudinal trunks. At section 190 the dorsal tracheae have moved 

 out laterally and are entirely lateral at section 240 (Fig. 4 of section 

 250, kit and rdt), where they lie on opposite sides of the gut. The 

 anterior or chief left (Idrti) and right (rdrti) dorsal rectal tracheae 

 are given off from the dorsal longitudinal trunks about section 250, 

 posterior part of segment VIII. These dorsal rectal tracheae run 

 mesad and supply the cokminar epithelium of the dorsal rectal 

 longitudinal fold (No. 12), (Figs. 4, and 6, Idrti and rdrti). By 

 the time they have reached section 260, posterior end of segment 



VIII, the dorsal trunks are really ventro-lateral in position with 

 respect to the gut. At section 320 they are again dorso-lateral in 

 position, and at section 328, caudad to the middle of segment IX, 

 they divide into the median (Imegt, rnicgt) and lateral (Icgt, rcgt) 

 caudal gill tracheae (Figs. 5 and 6). The lateral gill tracheae pass 

 to the ventral side of the gut and thence into the lateral gills. 



From the left median caudal gill trachea (Imcgt) small branches 

 (Idrtn) are given off to the dorsal rectal fold at section 345, segment 



IX, and section 362, segment X. About section 352 a small branch 

 (llrtn) is given off to the left ventro-lateral rectal fold. 



From the right median caudal gill trachea (rnicgt) a branch (rlrtn) 

 is given off to the right ventro-lateral rectal fold at section 356. 

 Two other small branches whose course could not be followed, are 

 also given off at about this point. 



In the anterior part of segment VII the lateral longitudinal tracheae 

 (lit, rlt) lie on opposite sides of the gut, beneath the dorsal trunks 

 (Figs. 1 and 6). They remain lateral in position as far as section 

 180, anterior part of segment VIII. A little caudad to this they pass 

 between the hypodermis and the ventro-lateral muscle masses 

 to the ventral side of the abdomen. They run thence caudad 

 beneath the gut (Figs. 6 and 4, lit, rlt), but never in contact with 

 it and giving off no branches to it, to section 373, segment X. Here 

 the right lateral longitudinal trachea (rlt) passes over to the left 

 side and joins (section 388) the left lateral longitudinal trachea 

 (lit), forming an anastomosis (arias); separating again almost immedi- 

 ately after (section 391, Fig. 5), they join respectively tracheae 

 rcgt and Icgt. 

 7 



