Fig. 57.—A, Cartilage of Trabeculæ of Ammocœtes, stained with Hæmatoxylin and Picric Acid. B, Nests of Cartilage Cells in Entosternite of Hypoctonus, stained with Hæmatoxylin and Picric Acid. (All references in this work to "Ammocœtes" or "Petromyzon" appear to refer to the species now called "Lampetra planeri".)