THE DOCTRINE OF IMMORTALITY 



Lepidosteus 



Lepidosteus 



Roof End. 

 Sub- germ Cav 



Sub-cerm. End., 



\Periph. End. \Vit End. 



FIG. 24. Diagrams to show the migration of sexual cells in four different verte- 

 brates. Arch, primitive intestine (archenteron) ; Int, intestine; Lat. Mes, lateral 

 mesoderm; Mes, mesothelium, or wall of the body cavity; Meson, embryonic kidney 

 (mesonephros); Myo, anlage of the muscle (myotome); Noto, primitive axis (noto- 

 chord); S.C, sexual cells in migration; W.D, renal, or Wolffian duct. After Bennett 

 M. Allen. 



