98 



PROCEEDINGS OF THE ACADEMY OF 



[March, 



Closed spiracles (Fig. 6, Sp. 7) connect with the lateral longitudinal 

 tracheae (rlt, lit) at sections 45-49 and 60, segment VII, where the 

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

 trunks {kit, rdt). There are closed spiracles {Sp. 8) also at the 

 corresponding points on the lateral tracheae in segment VIII, 

 sections 165 and 171. But in addition to the dorsal lateral con- 

 nectives, there originate here the tracheae which bifurcate at about 

 section 190 to form the right {rvs) and left {Ivs) visceral tracheae, 

 and the right (rlrti) and left {Urti) lateral rectal tracheae. The 

 latter may be considered as prolongations caudad of the visceral 

 tracheae (Figs. 6 and 4). 



The left visceral trachea {Ivs), as shown in Fig. 6, runs cephalad 

 as far as section 1, anterior end of segment VII. Between sections 

 190 and 155 it lies ventrad to, but not in contact with the gut (Fig. 

 3, Ivs); anterior to section 155 it assumes a lateral position (Fig. 1). 

 At section 120 the main trachea divides into three branches. One 

 of these supplies the left ventro-lateral fold (No. 8) of columnar 

 epithelium (Sect. 60). The third branch runs forward to the 



Fig. 6. Diagram of the hind-gut and rectal tracheae. The abdominal 

 segments are numbered in Roman numerals on the left side of the figure, the 

 microtome sections are numbered in Arabic on the right. The sections are 

 numbered in order (1-420) beginning at the anterior end of the hind-gut (anterior 

 end of segment VII) and proceeding caudad to the posterior end of segment X. 

 The short horizontal lines immediately above the Roman numerals indicate 

 the approximate boundaries of the segments. The meanings of the abbrevia- 

 tions designating the tracheae are given below. 



Those portions of the lateral longitudinal tracheae which lie ventrad to 

 the gut are represented by lines of alternating dots and dashes, thus .-.-.-.-.-. 

 This has been done to distinguish them from the tracheoles which either run 

 along, or pass into the ventral rectal walls, and are represented by broken lines, 



thus . The tracheoles which run along or pass into the dorsal rectal 



wall are represented by solid lines. 



Abbreviations. 



anas, anastomosis. 



die, transverse tracheae connecting the 



dorsal and lateral longitudinal 



tracheae. 

 Icgt, left caudal gill trachea. 

 /c///i, anterior or chief left dorsal rectal 



trachea. 

 Idrln, posterior or secondary left dorsal 



rectal trachea. 

 Idt, left dorsal longitudinal trachea. 

 lit, left lateral longitudinal trachea. 

 llrti, anterior or chief left lateral rectal 



trachea. 

 llrtu, posterior or secondary left lateral 



rectal trachea. 

 Imcgt, left median caudal gill trachea. 

 Irs, left visceral trachea. 



r, rectum. 



rcgt, right caudal gill trachea. 



rdrti, anterior or chief right dorsal rectal 

 trachea. 



rdt, right dorsal trachea. 



rlrti, anterior or chief right lateral rec- 

 tal trachea. 



rlrtn, posterior or secondary right lat- 

 eral rectal trachea. 



rlt, right lateral trachea. 



rtncgt, right median caudal gill trachea. 



rvs, right visceral trachea. 



sp7, unopened spiracle of the 7th ab- 

 dominal segment. 



sp8, unopened spiracle of the 8th ab- 

 dominal segment. 



