One day, as I watched some hundreds of Adélies bathing in an open lead, suddenly the back of an enormous killer-whale (_Orca gladiator_) rose above the surface as it crossed the lead from side to side, appearing from beneath the ice on one side and disappearing beneath it on the other. To my surprise, not the slightest fear was shown by the birds in the water. Had this beast been a sea-leopard, there would have been a stampede, and every bird have leapt from the water on to the sea-ice. On this evidence I formed the opinion that in all probability killer-whales do no harm to Adélie penguins; later I saw it confirmed, when a school of killers shaved close past several floes that were crowded with Adélies, and made not the least attempt to get at them, as they might so easily have done by upsetting the floes. Very probably this is because the agile bird can escape with such ease from the ponderous whale, and fears it no more than a terrier fears a cow, though he thinks twice before coming within reach of its jaws. [Illustration: Fig. 55. "WITH GRACEFUL ARCHING OF HIS NECK, APPEARED TO ASSURE HER OF HIS READINESS TO TAKE CHARGE" (Page 90)] When the sea-ice had gone out, leaving open water right up to the ice-foot, a ledge of ice was left along the western side of the rookery, forming a sort of terrace or "front," with its sides composed of blue ice, rising sheer out of the water to a height of some six feet or more in places. From this point of vantage it was possible to stand and watch the penguins as they swam in the clear water below, and some idea was formed of their wonderful agility when swimming beneath the surface. As they propelled themselves along with powerful strokes of their wings, they swerved from side to side to secure the little prawn-like euphausia which literally swarm everywhere in the Antarctic seas, affording them ample food at all times. Their gluttonous habits here became very evident. They would gobble euphausia until they could hold no more, only to vomit the whole meal into the water as they swam, and so enlightened start to feast again. As they winged their way along, several feet beneath the surface, a milky cloud would suddenly issue from their mouths and drift slowly away down stream, as, without the slightest pause in their career, they dashed eagerly along in the hunt for more. When a penguin returned to his mate on the nest, after his jaunt in the sea, much formality had to be gone through before he was allowed to take charge of the eggs. This ceremony of "relieving guard" almost invariably was observed.