Being furnished with both kinds of respiratory organs, it can breathe equally well on land or in the water. It has a broad, flat head, blunt nose, and eyes situated near the muzzle. Though living so much in the water, its toes are not connected by intermediate membranes--indeed, they appear only to be intended for service on shore--its tail, nearly as long as its body, serving as a propeller in the water. PART TWO, CHAPTER TWO. CENTRAL AMERICA. Leaving the continent of North America, which may be said to terminate at the southern end of Mexico, we enter that extremely irregular portion of land which, now widening, now narrowing again, stretches in a south-easterly direction till it unites with the southern half of the American continent at the Isthmus of Panama. We find in Central America three marked centres of elevation. The first we reach is the great plain, nearly 6000 feet above the level of the sea, on which the city of Guatemala is situated. Numerous volcanic peaks rise from its midst; from it also flow several large rivers, some falling into the Gulf of Mexico, others eastward into the Gulf of Honduras, while smaller streams send their waters westward into the Pacific Ocean. The banks of these rivers are mostly covered with the richest tropical vegetation--the scenery of the river Polochie in Guatemala being especially beautiful. Another high plain occupies the centre of Honduras, and extends into the northern part of Nicaragua. From it also rise numberless streams, some emptying themselves into the Caribbean Sea, and others into the Lakes of Nicaragua and Managua. Further south rises the volcano of Cartago. Here the Cordilleras resume their general character of a vast mountain barrier, but once more sink down into low ridges as the chain passes through the Isthmus of Panama. As in South America, the Cordilleras run close along the Pacific coast. In consequence, the rivers which flow from their heights have a long course on the Atlantic side, and have carried down a large quantity of alluvial soil. Here, too, rain falls in greater or lesser quantities throughout the year. The vegetation is consequently rank, and the climate damp, and proportionately unhealthy. As the trade-winds blow from the north-east, the moisture with which they are saturated is condensed against the mountainsides, and flows backwards towards the Atlantic. The Pacific slope is, therefore, comparatively dry and salubrious--as indeed are also the elevated table-lands of the interior.