PLATE 1 



EXPIAXATIOX OF FIGURES 



1 Tarantula palmata. Saccule of the coxal gland. X 175. The drawing 

 is outlined from a photograph, the cells being drawn in semi-diagramatically, 

 to show more clearly than is possible in photograph the differences between 

 the cells of the saccule, the collecting duct and the labyrinth. The lumen of 

 the saccule is broken up into channels by blood capillaries or rather lacunae) 

 which push in the walls, and thus increase the surface of the saccule. In the 

 diagrams this feature of th saccule is not shown. S, saccule; CD, connecting 

 duct; CL, labyrinth; ET, commencement of exit tubule; M, muscle and con- 

 nective tissue indicated by horizontal broken lines; BC, blood capillaries indi- 

 cated only by vertical broken lines; GL, suboesophageal ganglion. 



2 Vejovis flavescens. Photograph of coxal gland of scorpion. X 100. With 

 the help of figure 1 the constituent parts can be made out. In the center is the 

 saccule; its lumen, broken up by inhanging capillaries, opening on the right 

 into the labyrinth, whose tubules in this case completely surround the saccule 

 except at one point (CA) \vhere the blood supply enters. At ET is the com- 

 mencement of the exit tubule, but the tubule itself is not shown. The coxal 

 gland rests posteriorly (right) upon the diaphragm D which separates the 

 cephalothorax from the abdomen. C, caeca of the intestine; .V, nerve supply- 

 ing appendage \T; M, muscle; CA, coxal artery; ET, exit tubule; D, diaphragm. 



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