TYPE ARACHNID A. 443 



uated at the posterior end of the mid-gut. The digestive 

 gland is a large five-lobed structure which empties through 

 several ducts into the mid-gut. 



The nervous system consists of a syncerebrurn lying 

 above the oasophagus and giving rise to nerves for the e3 r es 

 and for the chelicerse. It is connected with a suboesophageal 

 mass from which the pedipalps and the three anterior legs are 

 innervated, the fourth pair of legs receiving its nerves from a 

 pair of distinct ganglia separated only by a short distance 

 from the subcesophageal mass. Behind this in the abdomen 

 is a chain consisting of seven pairs of ganglia united by long 

 connectives. The eyes vary in number from two to six pairs, 

 one pair being situated on or near the median line, while the 

 others are lateral. 



Coxal glands occur in connection with the third pair of 

 legs, and the heart is an elongated structure lying in the an- 

 terior portion of the abdomen and possessing eight pairs of 

 ostia. 



The Scorpions are viviparous. The ovaries are situated 

 in the anterior abdominal region and are elongated, that of 

 one side of the body being united with the other by several 

 transverse connections. The oviducts, which are short, serve 

 as uteri, and open to the exterior by a single median opening 

 situated on the ventral surface of the first abdominal segment. 

 The testes consist of four tubes, those of the same side being 

 connected by transverse anastomoses, and unite together to 

 open into a protrusible penis, accessory glands, vesiculae sem- 

 inales, occurring in connection with each vas deferens. The 

 single genital orifice occupies the same position as in the 

 female. 



The Scorpions are confined to the warmer regions of the 

 globe, but few genera being known. Of these the genera Eu- 

 scorpius and Buthus are perhaps the commonest. 



2. Order Pseudoscorpionida. 



This order includes a number of small forms which are 

 found under the bark of trees or among dead leaves or moss, 

 one genus, Chelifer (Fig. 202), occurring occasionally between 



