414 ME. H. M. BEENAED ON THE Cn.EEJSTETID^. 



which extends backward in tlie median line to form an arch over 

 the sucking apparatus, and is an extension backward of the 

 dorsal surface of the labrum. The lateral expanding muscles are 

 attached to the outer sides of the coxal joints of the pedipalps. 

 In Galeodes this sucking apparatus is not so specialized, and 

 the oesophagus can be expanded and contracted almost along the 

 whole beak. Ohisium, therefore, in the formation of its mouth- 

 parts, comes halfway between Galeodes and the Scorpion, which 

 latter has no freely projecting beak, but has a small specialized 

 sucking apparatus in the same position as in Ohisium. 



On leaving the sucking apparatus, the oesophagus again 

 narrows to pass through the central ganglionic mass, widening 

 again at once into a great system of diverticula which fill the 

 whole body (fig. 6). There seem to be two pairs of primary 

 diverticula. The first pair must be subject to fluctuations in 

 size, as they sometimes reach to the dorsal surface, and at others 

 lie beneath the massive coils of the spinning-glands (fig. 9), 

 which, as we shall see, are very differently developed at difierent 

 times. This first pair fills all the space in the cephalothorax not 

 occupied by other tissues. It must be considered as the equiva- 

 lent of the four pairs which typically belong to the four posterior 

 cephalothoracic segments in Arachnids. The fusion of the four 

 leg-bearing segments above described will account for the fusion 

 of the four pairs of originally separate diverticula. In Scorpio 

 the four pairs of diverticula have also fused to form one pair, 

 this being due to the longitudinal compression of the whole 

 cephalothorax. 



The second pair is the more important. Its two branches run 

 laterally the whole way down the dorsal surface of the abdomen, 

 sending down secondary diverticula laterally and. ventrally. 

 These secondary diverticula are due to the constrictions caused 

 by the six posterior pairs of dorso-ventral muscles (fig. 6). The 

 muscular passages thus formed between the secondary diverticula 

 . will be referred to again. About the same place where these 

 two diverticula diverge, there is a median ventral primary diver- 

 ticulum, A similar median ventral diverticulum has been described 

 by Schimkievitch * and Bertkauf in the Spiders. 



* " L'Anatomie de I'Epeire," Ann. d. Science^ Nat., Zool. xvii. (1884). 

 i' " Ueber den Bau und Function der sog. Leber bei den Spinnen," Arch. f. 

 Mikr. Anat. 23 Ed. (1884). 



