The Caudal Heart of the Eel a Lymphatic Heart.--Effect of the Force with Which the Lymph-Stream Is Propelled Therefrom on the Flow of Blood in the Vein into Which the Heart Opens.--Explanation of the Appearance of Blood Propelled in Successive Drops, as If from the Heart, along the Caudal Vein.--Influence Which the Force of the Lymph-Stream from the Heart Exerts in Accelerating and Promoting the Flow of Blood in the Caudal Vein.