PHYLUM ARTHROPODA 



373 



illae) ; it serves for the ingestion of juices only, since spiders do 

 not eat solid food. 



The abdomen is connected by a slender waist with the cephalo- 

 thorax. Near the anterior end of the abdomen on the ventral 



FIG. 314. Diagram of a spider, Epeira diademata, showing the arrange- 

 ment of the internal organs. /, mouth; 2, sucking stomach; 3, ducts of liver; 

 4, so-called malpighian tubules; 5, stercoral pocket; 6, anus; 7, dorsal muscle 

 of sucking stomach; 8, caecal prolongation ot stomach; Q, cerebral ganglion 

 giving off nerves to eyes; 10, subcesophageal ganglionic mass; n, heart with 

 three lateral openings or ostia; 12, lung sac; 13, ovary; 14, acinate and pyri- 

 form silk glands; 75, tubuliform silk glands; 16, ampulliform silk gland; 

 i/, dendriform silk glands; 18, spinnerets; IQ, distal joint of chelicera; 20, poison 

 gland; 21; eye; 22, pericardium; 23,' vessel bringing blood from lung sac to 

 pericardium; 24, artery. (From the Cambridge Natural History.) 



surface is the genital opening, protected by a pair of appendages 

 which have fused together to form a plate called the cpigynum 

 (Fig. 313). On either side of the epigy- 

 num is the slit-like opening of the respir- 

 atory organs or lung books (Fig. 313; 

 Fig. 314, 12). Some spiders also possess 

 trachea which open to the outside near 

 the posterior end on the ventral surface 

 (Fig. 313). Just back of the tracheal 

 opening are three pairs of tubercles or 



SpinilCretS (Fig. 313; Fig. 314, l8] , Used and pencil consisting of 



for spinning threads. The anus (Fig. 



314, 6} lies posterior to the spinnerets. Hermann.) 



FIG. 315. End of foot 



