LIST OF ILLUSTRATIONS xvii 



PAGE 



FIG. 66. A Cell of the Nervous Reticulum of a Coelen- 



terate 203 



FIG. 67. Side View of the Body of the Ctenophore, 



Pleiirobrachia 213 



FIG. 68. An Epithelio-Muscle Cell ("Neuro-Muscle 



Cell") of Hydra 238 



FIG. 69. Diagram of Simple Multicellular Arcs . . 239 



FIG. 70. Diagrammatic Dorsal View of the Upper End 



of the Spinal Cord of Larval Amblystoma . 253 



