Russian aviation site "Wings Palette" has some great pictures of the Dornier Do J Wal in various livery schemes. Browse through the gallery and you'll see there was a huge amount of variation in hull and engine configurations over the lifetime of the aircraft. This particular plane is representative of the Wals used by Chile for exploration and mapping missions over the southern part of the country.
This closeup shot gives you a better look at the nose of the plane. That small propeller pod attached to the hull is an air driven generator for the radio set. Like the planes from "At the Mountains of Madness" this model was intended for very harsh and cold conditions. What's interesting is that the aircraft isn't sealed, a trait it shares with the planes used on Amundsen's arctic flight. Why would you expose the interior of a cold weather aircraft to frigid open air conditions?
The answer is condensation. Sealed metal hulled aircraft could have serious problems with water condensing and then freezing on the interior of the hull. The problem could be solved by using heat exchangers to warm low humidity exterior air and vent it inside the hull, but the equipment was prone to breakdowns and imposed a significant weight penalty.