Coxal glands of the Arachnids. 233 



and their cells ; the constituent parts in their order from the terminal 

 part to the exterior being- designated as the saccule (S), the col- 

 lecting tubule (CT), the labyrinth (CL), the bladder or vesicle (F) 

 and the exit tubule (ET) leading to the outlet (0), 



The typical cells of the labyrinth coils have a striated base in 

 which the cell outline is lost, so that the striated layer of the cells 

 appears continuous (photo 5 b). Directly upon the striated layer or 

 immediately beneath its border, but never at its base, lie the nuclei, 

 generally very large and prominent with much chromatin (photo 1), 

 but the variations are considerable ; the cell nuclei of some scorpions, 

 and more particularly of the solifugae being extraordinarily minute 

 (photo la). 



That part of the cell cytoplasm lying above the striated border 

 may be extensive, forming large well defined columnar or cubical 

 cells (photo 10), or the cell surface may be greatly worn down so 

 that the nuclei may appear to lie upon the striated border with 

 only fragments of cytoplasm attached to them (photos 15 a CL and 22). 



The typical saccule which is commonly held to represent the 

 last remnants of the coelom, does not form definite coiled tubuleJi 

 like the labyrinth, but is actually of the nature of a sac, indented 

 in every direction by blood capillaries, which penetrate into the sac 

 and hang- in it; the very thin walls of the sac being lined intern- 

 ally with a delicate epithelium which may be flattened so as to 

 resemble an endothelium. The capillaries therefore would seem to 

 serve the same purpose as the glomeruli of the vertebrate kidney 

 and may be referred to as glomeruli (photo 30 GLR). The 

 capillaries however can hardly, strictly speaking, be considered as 

 such. They are simply lacunae of the hemolymph system without 

 any walls of their own, so that nothing lies between the body fluid 

 and the lumen of the saccule, except the thin wall of the saccule 

 itself with its lining epithelium. 



At a certain point in the saccule the lumen, freeing itself from 

 the inhanging capillaries, becomes dilated, forming a central lumen 

 WSL) and from this central lumen of the saccule there runs a 

 short duct, or collecting tubule (CT) lined with epithelium (photo 9 b) 

 which then passes into the labyrinth (CL); the change from the 

 epithelium of the duct to the striated epithelium of the labyrinth 

 being very abrupt. 



The exit tubule is very narrow, lined with chitin and evidently 

 formed by an involution of the external surface, the cells beneath 



16* 



