272 



THE OLD MOUTH AND THE NEW. 



Fro. 179. 



Fit;. ISO. 



FIGS. 179 AND 180. Diagrams showing the location of the principal viscera, such as the enteric pouches, coxal 

 glands, malpighian tubules, lung books and gills. A, Scorpion; B, spider. 



FIG. 181. FIG. 182. 



FIGS. 181 AND 182. Hypothetical forms leading to the condition in vertebrates. 



