There were also sooty terns and gannets. It was interesting to watch the careful way in which the latter guarded their eggs, placed in holes on the ground. Wishing to make their offspring hardy, they do not build nests for them, I suppose; or, perhaps, the warmth of the rock assists the process of incubation. There were probably a greater number of tropic birds than of any others. They would not got out of our way as we walked along, allowing us to shove them over rather than move. We literally also took their eggs from under them, without their attempting to make any defence. This apathy, as we called it, we thought arose from stupidity, but the doctor examined one of them, and showed us how weak its legs were, while its feet were adapted only for swimming. Its wings, however, were very long and powerful. Therefore, had it been up in the air, or skimming along over the summit of the waves, it would probably have acted in a very different way. "Never judge of people till you know the sphere of life in which they have been accustomed to move," remarked the doctor. "A really sensible, clever man, may appear very stupid and dull, just as these poor birds do, simply because he is out of his element." The tropic bird is a species of gull, about the size of a partridge. It has a red bill and legs. The feathers are white, tipped with black, and the back is variegated with curved lines of black. The tail consists of two long, straight, narrow feathers, almost of equal breadth during their whole length. Their flight is most graceful--they glide along with scarcely any perceptible motion of the wing. They return every night to roost on land. They live entirely on fish. The natives of the South Sea Islands ornament their persons with their feathers. We saw a number of snakes, but none of them attempted to bite us; and the doctor said from their appearance that he did not believe them to be of a venomous character. Whenever we went near the water among the rocks, we saw large fish darting about, of every colour and shape; huge, long eels gliding in and out between the rocks, and fierce, voracious sharks pursuing their prey. There were a great variety of molluscs; indeed, the whole shore was composed of shells. We naturally thought that the shells were empty; but as we watched them, thousands of them began to move, each tenanted by a soldier-crab, and a whole army of them slowly advanced out of the sea and marched across the land, devouring all the insects they encountered in their progress. Now and then two of them would stop and have a fight over a beetle or a spider, when perhaps a third would step up and carry off the cause of dispute. We found the spiders' webs stretching in every direction between the bushes. The spiders themselves were great, ugly, black fellows, very disagreeable to look at, and still more unpleasant when we found them crawling over our faces.