Coxal glands of the Arachnids. 



251 



It is obvious tliat when tliese muscles are contracted the walls 

 of the saccule would be pulled out, the lumen would become distended, 

 and fllled with fluid filtering in through the walls. On relaxation 

 of the muscles, the saccule would tend to collapse upon itself, and 

 press upon the contained fluid which would thus be forced through 

 the coUecting tubule into the labyrinth. 



To increase the 

 extensibility and also ' 



no doubt to strengthen 

 the walls of the sac- 

 cule, they are rein- 

 forced internally by 

 a thick layer of 

 spongy cellular tissue 

 (photo 33), between 

 the cells of which 

 run innumerable fine 

 flbres, which may be 

 extensions of the 

 muscle flbres, but the 

 flbres themselves do 

 not appear to be con- 

 tractile. Although the 

 cells of the spongy 

 tissue have lost all 

 appearance of epi- 

 thelium they are pro- 

 bably derived frora 

 the original epithelial 

 lining cells of the 

 saccule. 



There is a con- 

 siderable lumen (CSL) 

 in the center of the 

 saccule, and pouches 

 from the central lumen 

 extend into the spongy 

 tissue on all sides (photos 34, 34 a, 34 b). 



Although this part of the organ has undergone such striking 

 modification that by itself it could no longer be recognised as the 



Galeodids 



Solpugids 



Diagram D. 



Showiug an outline of the coxal glands aud the 

 way in which a second exteusion posteriorly of the 

 labyrinth sac in the Solpugids has led to the change 

 from SL to GL being removed for sonie distance 

 from the main part of the gland. In the Solpugids 

 also the coiling of the labyrinth tubule is much more 

 complicated than in the Galeodids. 



