248 B. H. Buxton, 



On comparing the photographs of the labyrinth of group 1 

 (photos 21, 22) with those of group 2 (photos 26, 27), it will be 

 observed that although the tubules of group 1 are very much 

 shortened as compared with those of the Theraphosids, yet the 

 striation is very highly perfected ; more so in fact than in any of the 

 other Arachnids, except towards the anterior part of the internal 

 tubule in the neighborhood of the saccule (photo 24), where the striated 

 part appears somewhat reduced and there is a tendency towards 

 vesicular enlargement. It seems probable therefore that the ex- 

 cretory functions of the labyrinth of group 1 have not been in any 

 way impaired, whereas in group 2, they have been entirely or 

 almost entirely lost, and possibly, as suggested by Bernard, trans- 

 ferred to the production of silk. 



Group 3. Epeirids, Theridiids, Pholcids, 



F i 1 i s t a t i d s. 



In this group, the members of which are all expert web spinners, 

 the labyrinth reaches its extreme limit of simplification. Practically 

 nothing is left of this part of the gland but a short bladder (F) 

 leading to the exit tubule (ET); the bladder opening above im- 

 mediately into the saccule (S) with its inhanging glomeruli (GLR) 

 (photos 29 to 32). The walls and epithelium of the labyrinth have 

 become thinned down throughout, and so fused with the saccule 

 that it is impossible to distinguish between them. 



The well preserved condition of the saccule however and the 

 well marked opening on the external surface, show clearly that 

 the gland must be functional, although it would obviously be 

 impossible to homologise such an organ with that of the other 

 arachnids if it were not for the intermediate steps which can be 

 traced back to the Theraphosids through groups 2 and 1 of the 

 Araneae verae. 



Diagrams A and B show roughly in a general way the main 

 points of the difference and similarity between the coxal glands of 

 the Scorpions, pedipalps and spiders, and the description attached to 

 the diagrams will serve also as a summary for Part I. 



