PLATES.
| PAGE | |
| Development of a Calcareous Sponge (Olynthus) | [Frontispiece] |
| I.—Life History of a Simplest Organism | To face page [184] |
| II., III.—Germs or Embryos of Four Vertebrates | " [306] |
| PAGE | |
| Development of a Calcareous Sponge (Olynthus) | [Frontispiece] |
| I.—Life History of a Simplest Organism | To face page [184] |
| II., III.—Germs or Embryos of Four Vertebrates | " [306] |