Coxal glands of the Aracbnids. 245 



all of them there is au exit tubule with an outlet on the third 

 appendage fnnctional in the adult as well as in the immature. The 

 collecting tubule has been lost and the lumen of the saccule passes 

 directly into the labyrinth tubule. 



Group 1. Sicariids and Dysderids. 



The six-eyed Sicariids and Dysderids show the most primitive 

 condition of the labyrinth. Starting- from the main body of the 

 saccule opposite the third appendage, it runs posteriorly as a Single 

 straight tubule as far back as the sixth appendage where it turns 

 inwards, and then runs forward as a straight dilated tubule, inter- 

 nal to the first tubule, and along the endosternite to its outlet on 

 the third appendage (Diagram A). 



Diagram A. 



Coxal gland of group 1 of the Araueae verae. 



The saccule (S) opposite appendage III, leads into the straight external 

 tubitle {LET) which runs posteriorly as far as appendage VI Avhere it turns 

 and runs as the internal tubule (Lit) anteriorly to the outlet on appendage III. 

 Both [LET) and {LIT) are lined with striated epithelium. The vertical broken 

 lines indicate approximately the points through which transverse sections were 

 cut from different specimens and photographs taken (21 to 24). 



Since the labyrinth tubule running posteriorly from the saccule 

 is, in the true spiders, always external to the other, it may be 

 referred to as the external tubule (LET) and the tubule running 

 anteriorly to the exit, as the internal tubule (LIT), the two to- 

 gether composing the labyrinth. In Sctjtodes (Sicariid) there are a 

 few loops at the posterior end of the labyrinth, but these are wanting 

 in Loxosceles (Sicariid) and Dijsdera, in which the labyrinth simply 

 runs backwards and then forwards again, so that in transverse sec- 

 tions one sees two tubules cut across, the external one leading from 

 the saccule posteriorly; the internal one close to the endosternite, 

 being the return tubule to the exit (photos 21, 22). The labyrinth 

 cells have the usual striated base on which the large nuclei rest, 



