1918.] NATURAL SCIENCES OF PHILADELPHIA. 85 



rectal tracheae (rlrti and llrti). Each of these passes mesacl and 

 caudad and enters the lateral longitudinal rectal fold of its respective 

 side. The origin of the right lateral rectal trachea differs slightly 

 from that of Thaumatoneura as worked out by Calvert. Subdivision 

 of these tracheae occurs and some of the tracheoles enter the 

 epithelium. No anastomosis has been found here. A smaller 

 posterior rectal supply (llrtu and rlrtn), is received by the lateral rectal 

 folds from the left and right median caudal gill tracheae respectively. 

 Some of these tracheoles also enter the epithelium, but no anastomosis 

 occurs. 



A small posterior dorsal supply (Idrtn) is received by the dorsal 

 longitudinal fold and by the epithelium from the left median caudal 

 gill trachea. The corresponding (?) group on the right has been 

 traced laterad through and around the muscle fiber mass toward 

 the periphery of the body. 



The last two paragraphs show slight differences between Thaumci' 

 toneura and Argia talamanca. 



Calvert's statement for Thaumatoneura may be quoted here for 

 A. talamanca. "The only anastomosing tracheae which have been 

 discovered are the posterior terminations of the right and left [?] 

 lateral longitudinal tracheae which, assuming a ventral position, 

 meet on the mid-ventral line ventrad of the alimentary canal; in 

 this anastomosis {anas) take part also a branch from the right and 

 a branch from the left [?] lateral caudal gill trachea." The inter- 

 rogation marks signify an incomplete tracing in Argia talamanca 

 due to maceration of parts of the anastomosing tracheae from the 

 left side. 



I think I may say that all the tracheae, large and small, that 

 were traced possessed a black pigment that added materially to the 

 ease of tracing. As has been observed for Thaumatoneura, this 

 pigment presents the same appearance as that of the areas between 

 the three longitudinal folds of the rectal epithelium. 



For material, directions and suggestions in my work I am indebted 

 to Dr. P. P. Calvert, whose treatment of Thaumatoneura I have 

 followed for Argia talamanca. The sections studied were of "larva 

 No. 2," 9, from the "nearer waterfall," Juan Vinas, Costa Rica, 

 March 23-26, 1910, which died in attempted rearing; its condition 

 is, therefore, histologically poor. The locality has been described 

 by Calvert in his Thaumatoneura paper cited. 



