1 98 



THE EVOLUTION OF MAN. 



"Worms, we find an independent nerve-systein, distinct and 

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



Fig. 209. — Gastrnla of Gastrophysema (Gastrasad-class) . 



Fig. 210. — Transverse section through an embryonic Earth-worm : Jis, 

 skin-sensory layer; hm, skin-fibroas layer; iZ/, intestinal-fibrous layer; dd, 

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

 », nerve-ganglia; u, primitive kidneys. 



Fig. 211. — A Gliding Worm (RhdbdoccBlum). From the brain or ripper 

 throat ganglion (g) nerves (n) radiate tovfards the skin (/), the eyes (au), 

 the organ of smell (na), and the mouth (m) : h, testes ; e, ovaries. 



