398 ZOOLOGY 



oesophagus leads from this sac to a second enlargement, which 

 receives the ducts of a pair of salivary glands, structures 

 which are usually associated with a terrestrial mode of life. 

 The succeeding digestive portion of the alimentary canal re- 

 mains narrow ; it receives four or five ducts which convey the 

 secretion from a corresponding number of lobes of the liver. 

 The latter is a considerable gland which takes up a good deal 

 of space in the wide mesosoma, and even extends into the 

 narrow nietasomatic segments. One or two pairs of delicate 

 Malpighian tubes are present, and these have been recently 

 shown in one species to be developementally outgrowths from 

 the mesenteron ; a pair of these tubes are branched. A procto- 

 daeum is present, and ends in an anus situated ventrally at 

 the end of the metasoma. 



The heart in Scorpio, as in Limulus, consists of a median 

 tube of eight chambers ; it is continued backward in the scorpion 

 as a posterior aorta which traverses the metasoma. A pair of 

 valvular ostia open into the anterior end of each chamber, 

 and a pair of lateral arteries take their origin from the pos- 

 terior end of each division. The eight chambers lie in the 

 seventh to the thirteenth segments, the last containing two 

 chambers. From the anterior end of the heart a truncus 

 arteriosus leads forward; this vessel gives off two lateral 

 branches, which embrace the oesophagus and then unite into a 

 median artery which runs backward above the nerve cord. 

 In front of this ring the anterior aorta divides into two lateral 

 vessels and a median one, these supply the appendages of the 

 prosoma, the brain, and other organs. After passing through 

 the body, the blood collects in a ventral reservoir and passes 

 thence to the lung-books. Here it is oxygenated, and is then 

 conveyed by special veins back to the pericardium, and so 

 into the heart. The blood in Androctonus is, when oxygenated, 

 of a deep indigo blue, coloured by haemocyanin ; its corpuscles 

 are oval, and are remarkably large. 



The four pairs of oval stigmata, which are obliquely placed 

 on the sterna of the ninth, tenth, eleventh, and twelfth seg- 

 ments, lead into sacs, into the lumen of which project numerous 

 lamellae. These lamellae, of which there may be as many as 

 130, arise from a definite axis, which is for the most part 



