264 -B. H. Buxton, 



nephridium of Feripatus (1) the relative sizes of the component 

 parts are approximately given, but for the other figures it has 

 merely been attempted to indicate which of the original parts have 

 been preserved or lost without regard to their relative size. In the 

 scorpions and higher spiders we find a vesicular enlargement just 

 before the exit tubule is reached, but it does not appear that this 

 vesicle can be homologized with that of the typical nephridium in 

 Peripatus. In neither scorpions nor spiders is the vesicular enlar- 

 gement lined with cells differing from those of the labyrinth, nor 

 has it any regularity of shape. The vesicle (6) therefore in the 

 last figure of the diagram is drawn as "doubtful". 



If the hypotheses here suggested as to the origin of the coxal 

 glands are correct it would seem that the parent stock of the soli- 

 fugae must have been different from that of the other Arachnids 

 since they appear to have descended from a branch of the original 

 stock in which the salivary glands had become paramount, whereas 

 in the parent stock which gave rise to the other Arachnids, the 

 salivary gland of the second appendage had retrograded, and the 

 nephridia situated on the third to the sixth appendage had become 

 the most important; developing along lines similar to those of the 

 sixth and seventh appendages in Peripatus. 



So far as I am aware the new observations are: 



Scorpions. Blood supply to saccule from artery of appendage V. 

 Lymphatic organ wanting in Buthids but present in the other families. 



Pedipalps. Saccule and collecting tubule opening into laby- 

 rinth. Columnar cells in labyrinth of Tarantula confined to the 

 middle division. 



Spiders. T h e r a p h o s i d s. Two saccules, each with its col- 

 lecting tubule opening into the labyrinth, and two outlets. 



Araneae verae. Saccule and its communication with the 

 disappearing labyrinth. 



Solifugae. Modified saccule with pump and collecting tubule. 

 Outlet on appendage II with squirt and projecting sheath. 



Peripatus. Modified (secretory) portion of the labyrinth of 

 the typical nephridium (?). 



Modified nephridia of legs six to twelve in P. jamaicensis. 



Homology of the salivary gland in Peripatus with the coxal 

 gland of the solifugae. 



Homology of the coxal glands of the other Arachnids with the 

 large nephridia of Peripatus on legs four and five. 



