3'.)4 ZOOLOGY. 



segmented. In all Vertebrates above the lamprey, the verte- 

 bral column grows around the notochord, which finally 



FIG. 370. 



Fig. 374. Transverse section through the spinal cord of a calf, a, anterior, b, 

 posterior longitudinal fissure ; c , central canal ; d, anterior, e, posterior cornua ; f, 

 substantia gelatinosa; g, anterior column of the white substance; /i, lateral, i, pos- 

 terior column ; k, transverse commissures. After Gegenbaur. 



Fig. 375. Section through the vertebral column of Ammoccetes (lamprey). Ch, no- 

 tochord; c., chordal sheath ; m, spinal chord ; a, aorta; v, veins. 



Fig. 376. Section through the spinal column of a young salmon. Ch, notochord ; 

 cs, chordal sheath; m, spinal chord ; k, superior, k', inferior arch (rudimentary) ; a, 

 aorta ; v, veins. After Gegenbaur. 



forms the central portion of the bodies of the vertebrae, and 

 in the higher Vertebrates is wholly effaced; the centra or 



