244 B. H. BuxTON, 



outlet on the third appendage, but denies tlie existence of one on 

 the fifth, although the cells dip down very close to the surface. 

 ScHiMKEviTCH figures sagittal sections in which I have generally 

 found that the outlet on the third appendage is cleaiiy defined, but 

 to observe the whole exit tubule and outlet of the fifth appendage 

 in one field, it is necessary to have transverse sections. In sagittal 

 sections the course of the exit tubule on the fifth appendage must 

 usually be followed up from section to section and it is often diffi- 

 cult to determine if there is actually an outlet or not. Photograph 

 18 b is taken from the only sagittal section 1 have which shows the 

 exit tubule of appendage V in its entirety. It may be observed 

 that 18, 18 a, 18 c are all taken from transverse sections. 



ScHiMKEviTCH does not mention the saccule, and his specimens 

 were perhaps too young to show it clearly. I have myself been 

 unable to identify the saccules with certainty in specimens of Avi- 

 cularia from the cocoon, although in those of Eurypelma (photo 15) 

 at about the same stage of development it is already clearly defined. 



Brüntz (1904), so far as I can gather, is the only author who 

 mentions the existence of a saccule. He found it in Atijpus and 

 demonstrated that the cells of the saccule eliminate carmine, but 

 not those of the labyrinth. Beuntz was unable to obtain specimens 

 of the Theraphosids, but in a living DugesieUa hentsii from Texas 

 (given to nie by Dr. Petrunkevitch) inoculated with carmine and 

 killed three days later, the same results were noted as by Bruntz 

 for Atypus, namely that the cells of the saccule took up carmine, 

 but not those of the labyrinth (photo 20). Both of the saccules 

 were alike in this respect. 



The fact, however, that there are two saccules and two outlets 

 in the Theraphosids does not appear to have been recognised by 

 anyone. 



B. Araneae verae. 



In all the Araneae verae there is a Single saccule lying mainly 

 opposite the third appendage, but extending also posteriorly to about 

 opposite the fourth appendage. The thin walls of the saccule are 

 lined with delicate and sometimes flattened epithelium, and glomeruli 

 hang into its lumen in the usual way. The saccule therefore preserves 

 its typical appearance, but the labyrinth has become greatly reduced 

 and simplified. According to the degree of simplification of the 

 labyrinth the Araneae verae may be divided into three groups. In 



