658 



ZOOLOGY 



SECT. 



and oxygenates the blood which enters the interior of the laminae 

 from the ventral sinus. 



A pair of coxal glands, situated near the base of the fifth pair 

 of appendages, are, in the embryo Scorpion, represented by tubes 

 which, like nephridia, effect a communication between the body- 

 cavity and the exterior ; in the adult Scorpion the tube assumes 

 the form of a closed gland, and its function is quite uncertain. 



The nervous system is constructed on a plan which bears a 

 considerable resemblance to that of the Crayfish and that of the 

 Cockroach. There is a bilobed cerebral ganglion or brain (Fig. 536, 



Irn.) from which nerves are 



chel 



stoma 



salqlct 



he/} die 



given off to the eyes ; a nerve- 

 collar formed of a pair of 

 esophageal connectives unites 

 ventrally in a sub-wsophageal 

 ganglion, forming the anterior 

 part of a ventral nerve-cord 

 {ne. co.). The connectives and 

 sub-oesophageal ganglion give 

 rise to the nerves of the first six 

 pairs of appendages and of the 

 operculum, the pectines, and the 

 two following segments. The 

 first ganglion behind the sub- 

 cesophageal ganglion appears in 

 the eleventh segment (reckoning 

 the cephalothorax as made up 

 of six) ; behind which a ganglion 

 occurs regularly in each seg- 

 ment as far back as the fourth 

 of the post- abdomen. 



The organs of special sense 



are the eyes and pectines. The 



lateral eyes (Fig. 556) are 



similar in character to the 



simple eyes or ocelli of Insects. 



The two larger central eyes (Fig. 557) differ from them in having 



the retinal cells arranged in groups as in the compound eye, but 



resemble them in the presence of a single cuticular lens. 



Reproductive organs. — In the male the testes consist of two 

 pairs of longitudinal tubules united by cross branches. These 

 are connected with a median vas deferens, the terminal portion of 

 which, provided with accessory glands, is modified to form a double 

 penis ; its external opening is just behind the operculum, as 

 already noticed. There is an unpaired ovary, which is made up of 

 three longitudinal tubules with transverse connecting branches ; 

 the oviducts open on the operculum. 



Fig. 537. — Dorsal view of the internal organs 

 of Scorpion, chel. chelicera: ; hep. liver ; 

 hep. du. hepatic ducts ; inal. Malpighian 

 tubes ; mesent. mesenteron ; proct. intestine ; 

 sal . f/ld. salivary glands ; stomo. stomodajum. 

 (From Leuckart, after Blanchard.) 



