i 9 8 



THE EVOLUTION OF MAN. 



Worms, we find an independent nerve-system, distinct and 

 separate from the outer skin-covering. This is the " upper 



FIG. 209. Gastrnla of Gastroplivscnia (Gastroead -class). 



FIG. 210. Transverse section through an embryonic Earth-worm : 7is 

 skin-sensory layer; hm, skin-fibrous layer; df, intestinal-fibrous layer; dd> 

 intestinal-glandular layer ; a, intestinal cavity ; c, body-cavity, or Cccloma ; 

 n, nerve-ganglia ; u, primitive kidneys. 



FIG. 211. A Gliding Worm (Rhabdoccelum). From the brain or tipper 

 throat ganglion (g) nerves () radiate towards the skin (/), the eyes (a), 

 the organ of smell (r?a), and the month (m) : 7i, testes ; e, ovaries. 



