ANATOMY OF ARACHNIDS 



19 



The supraoesophageal ganglion, with its sense organs, need 

 not be considered as having any segmental value except in so 

 far as the ganglion for the chelicerae is concerned — a ganglion 

 which in the earliest stages is obviously suboesophageal and on 

 later development moves over and becomes fused with the 

 brain. 



Diagram 6 The ganglia of group II. Fig. 1 Frontal view of the ganglia of 

 the Solifugae. The five neuromeres of which the suboesophageal ganglion is 

 composed are indicated, and below is the large single abdominal ganglion, 

 connected by a nerve cord with the suboesophageal. 



Fig. 2 Frontal view of the ganglia of Koenenia. Resembling that of the 

 Solifugae, but showing three abdominal ganglia instead of a single one. 



The five anterior ganglia of the suboesophageal mass supply 

 appendages II to VI, which, with the chelicerae, represent the 

 six segments of which the cephalothorax is composed. This 

 number of segments of the cephalothorax obtains in all orders 

 of this group and leaves twelve abdominal segments to be ac- 

 counted for, each with its attendant ganglion. 



