242 B- H. BuxTON, 



ously along its length from the third to tlie sixth appendage in- 

 clusive (photo 13), but no saccule is yet visible. On passiiig to 

 sections more and more ventral the labyrinth breaks up into four 

 parts, one of which is opposite the posterior aspect of each of the 

 appendages from the third to the sixth ; showing therefore, that there 

 are four distinct dips of the labyrinth toward the ventral surface 

 (photo 13 a). The two succules on the third and fifth appendages 

 respectively now make their appearance, lying a little external to 

 the labyrinth tubules, but they are quite distinct from each other. 

 I have been unable to trace any saccule on the dip of the sixth 

 appendage, although there is some evidence of a saccule on the 

 fourth appendage, but no collecting tubule or change to labyrinth 

 in connection with it. It appears to be rather an outlying part 

 of the saccule of the third appendage, and not to have an indepen- 

 dent existence. 



Examining sections still more ventral it is found that the dips 

 of the labyrinth tubules on the fourth and sixth appendages end 

 blindly not far from the ventral surface, while those on the third 

 and fifth pass on to their respective exit tubules and outlets, both 

 of which are functional in the adult as well as in the young. These 

 four . dips with the two saccules and two exits can also be readily 

 traced in sagittal and transverse sections. 



The dips of the labyrinth on the fourth and sixth appendages 

 seem to indicate that primarily there were outlets at these points 

 also. The dip on the posterior aspect of the sixth appendage in 

 particular shows in the young Avicularia from the cocoon, a very 

 marked string of labyrinth cells (the lumina of the tubules in these 

 specimens are barely apparent) extending right up to the external 

 surface (photo 14). 



This extension is so clearly defined that for some time I thought 

 that there must be an outlet there also, but careful search through 

 all the specimens has failed to show any. 



The saccules (S), as can be seen from the photographs (15, 15 a, 

 15 b, on third, and 16, 16 a, 16 b, on fifth appendages) present the 

 typical appearance as described for the scorpions and pedipalps 

 with the inhanging glomeruli (GLB) and the collecting tubule (CT), 

 passing abruptly into the labyrinth (CL). In the labyrinth the 

 cells have the usual striated base upon Avhich rest enormous deeply 

 stained nuclei; the cytoplasm in places being worn down to the 

 nuclei and in other places forming large well outlined cubical cells. 



