SPIDER GOSSIP. 23 



figure). The upper parts continue straight along and supply the 

 jaws, etc. ; the lower turn at right angles, and underneath the 

 throat divide once more^ this time into six or more vessels each. 

 Two arteries run backward to the abdomen, two forward to the 

 under lip, and four on a side supply the four pairs of legs. In 

 the drawing these last are shown as four tiny circles, being cut at 

 right angles to their length. The blood is not applied to the 

 various organs by means of " capillaries " (very thin tubes), as in 

 higher animals, but issues from the arteries, and touches the parts 

 directly. Neither are there veins to convey it back to the heart. 

 It is obliged, as we may say, to get back the best way it can, in 

 the spaces between the tissues and organs. Insects are said to 

 have neither arteries nor veins, and so in having arteries spiders 



Fig. 5. — Cross section of Head-thorax of Spider, cut through 

 at the place where the dotted line connects the letters 

 ph with the organ they indicate in Fig. 1. Magnified 

 ten diameters. 



are more highly organised. But before getting back to the heart, 

 the blood, as we all know, requires to be freshened by contact with 

 air, either in the lungs or by some other method. Insects have 

 tubes full of air, called trachea, running throughout the body, and 

 open to the outer air by means of holes in the sides of the body. 

 Here again a spider is considered more highly organised than a 

 true insect. Its blood is freshened by a pair of little organs best 

 called " gills." Some spiders are said to breathe by trachea too. 

 This is not accurate, the so-called trachea being modifications of 

 the ordinary gills. These gills are situated on the under side of 

 the abdomen where it joins the head-thorax, and they open to the 

 outer air by two little transverse slits. They are placed one on 



