Survey of the Animal Kingdom 325 



Phylum 12. Chordata (kor-da'ta) (L. chordatus, having a rodlike chord) 



General Characteristics 



A dorsal, rodlike notochord (Gr. noton, back or dorsal; chorde, chord) is 

 present as a cartilaginous or bony structure at some stage of life. A central, 

 tubular nerve cord is located dorsally. Paired pharyngeal clefts (gill slits) are 



Fig. 136. — Horseshoe crab or king crab (Limulus polyphemus) of the class Arach- 



noidea, phylum Arthropoda (dorsal view). 



Heart 



Pericardium 



Sucking Stomach 

 Dorsal Muscle Of Sucking Stomach 

 Eve Cerebral Ganglion 



Malpighian Tubules 

 StercoralPocket 



Poison Glan 



Pedipalp 



Dendriform Silk Glands 



Anus 



Spinneret 

 And 

 Pyriform Silk Glands 

 Ampuliforra Silk Glands 



Tubuliform Silk Glands 



Fig. 137. — Spider, shown diagrammatically from the side, somewhat enlarged. 

 (From Metcalf: Economic Zoology, published by Lea & Febiger. ) 



present for respiration purposes at some stage. In certain species, these clefts are 

 no longer visible, as such, in the adult. The coelom (body cavity) is well de- 

 veloped. Bilateral symmetry is generally characteristic. The animals are triplo- 

 blastic (ectoderm, mesoderm, entoderm). The body is metameric (segmented). 



