234 B- H. Büxton, 



the cliitin resembling tliose of the hypodermis. The arrangement 

 of muscles around the exit tubule seems to indicate that the outlet 

 can be closed and opened at will. Just before reaching the exit 

 tubule, the labyrinth tubule straightens out and sometimes becomes 

 dilated, forming a vesicle or bladder (Patten's "end-sac" in Limulus). 



1. Scorpioiis. 



The coxal glands of the scorpions were first described by 

 Lankester who recognized the tubules lined with striated epithelium 

 (the labyrinth), and a medullary portion, enclosed by the tubules. 



The medullary portion was first recognized by Marchal (1892) 

 as the saccule, from which the collecting tubule passes into the 

 labyrinth. Maechal speaks of the lacunae of the saccule and the 

 lacunae of the hemolymph System, which together form the medullary 

 portion, but the saccule possesses definite walls lined with epithelium, 

 so it would hardly seem correct to describe its lumina as lacunae. 



Marchal also drew attention to the homology between the 

 coxal glands of the scorpion, and the green giands of the decapods, 

 which also have a saccule and a labyrinth distinct from each other. 



The coxal gland of the scorpion is very compact, situated oppo- 

 site the bases of the fifth and sixth appendages ; its posterior border 

 lying on the anterior surface of the diaphragm (D) which separates 

 the cephalothorax from the abdomen (photo 1, 3). The Saccule {S} 

 is surrounded and enclosed by the coils of the labyrinth tubules 

 {CL) except at one point where the blood supply enters the organ. 

 Opposite the entrance of the coxal artery the central lumen of the 

 saccule passes into a Short, ill defined collecting tubule, connecting 

 with the labjTinth (Photos 1, la, for a general view, and Ib, Ic, 

 for the details of the changes). 



The tubules of the labyrinth form complicated coils and finally 

 end in a straight somewhat dilated tubule, which may be regarded 

 as the bladder. The bladder passes into a very narrow straight 

 exit tubule (ET, photo 2) lined with chitin, and obviously derived 

 from the external surface. The outlet appears to be functional even 

 in the adult in spite of much that has been writteu to the contrary. 



Diagram Bl indicates roughly the position of the coxal gland 

 in cephalothorax and the plan on which it is constructed. 



At the base of the sixth appendage there is a distinct dip of the 

 labyrinth tubule toward the surface, which iu the embryo scorpion 



