6 B. H. BUXTON 



of the saccule is increased by blood capillaries which push in 

 the wall of the saccule and break up its lumen into tortuous 

 channels (figs. 1 and 2). The elongated and flattened saccules 

 of Thelyphonus have sufficient surface of themselves and are 

 not invaded by capillaries in this way. The saccule of Thely- 

 phonus appears tubular in sections, and the tubules can be dis- 

 tinguished from those of the labyrinth only by the nature of the 

 epithelium lining the walls. The cubical epithelium of the sac- 

 cule has very delicate outlines and the cytoplasm often contains 

 solid particles — ^probably urates — ^which are never found in the 

 coarser striated epithelium of the labyrinth. On injecting car- 

 mine the particles are taken up by the cells of the saccules, but 

 never by those of the labyrinth. 



Diagram 2 Coxal gland of the Thelyphonides. Two saccules, one on seg- 

 ment IV, and another on segment V, with a labyrinth common to both saccules 

 and an outlet behind appendage III. S, saccule; CL, labyrinth; ET, exit tubule. 



From each of the two saccules of Thelyphonus a short but 

 wide collecting duct leads into a tubule of the labyrinth directed 

 posteriorly, so that the tubule from the saccule on segment V 

 extends posteriorly into segment VI where it forms coils which 

 ultimately pass forward again. Similarly the tubule from the 

 saccule on segment IV extends backwards into segment V where 

 it joins the main coils. The coils coalesce at some hitherto un- 

 determined point, and the coiled labyrinth tubule passes forward 

 to a point opposite the anterior saccule, where the coiling comes 

 to an end and the labyrinth runs forward as a single straight 

 tubule to its outlet just posterior to appendage III (diagram 2). 



The outlet, therefore, is in the same position as that of Taran- 

 tula, but the saccules, instead of being in segment III only, or 

 in III and V as in the Charontini, are in segments IV and V. 

 Moreover, the entire coxal gland is evidently formed by fusion 



