It was in the year 1870 that the _Ceratodus_, or the “Barramunda,” as the Australian natives call him, was discovered in the rivers of Queensland; and since then he has become very famous, for, more than any of the others, he is like the fishes of long ago. He is a lumpy fish, sometimes as much as six feet long, with a gristly cord for a backbone. His body is covered with large rounded scales, and he has a broad fringe round his pointed tail. His fins are more like paddles than fish fins, having several joints, and he uses them, together with his fringed tail, to flap along in the water, or even to wander over the reedy flats at night, chewing the weeds with his broad ridged teeth. And as he flaps along, from time to time, when the water is too muddy for his liking, he comes up to the top, and with a great gulp swallows air into the air-chamber. But before he can do this he must send out the bad air within, and in doing so he gives a grunt which is often heard far away at night in those still Australian wilds. He need not come up for air-breathing, however, if the water is pure, for, strange to say, the whole course of his blood can be altered to suit his wants. When he can get clear water to breathe through his gills the blood flows to them to be freshened, and his air-bladder simply takes in gas from the body as it does in other fishes, and wants feeding with good blood. But when he comes up to breathe then the blood is carried the other way, and comes to the air-bladder to be freshened. And now if we want to read the history of all these strange forms, you must let me take you by the hand and lead you in imagination back, back through millions of years, to a time so long ago that we cannot even count the ages between. As we recede from our own day we shall leave behind us all the kinds of plants and animals we now know so well, and meet with strange kinds only bearing a general resemblance to them. After a long journey of thousands and thousands of years, in which the plants and animals, and even the very shape of the continents and islands, have gone through many changes, we shall get back to the time when the lime-builders were forming thin layers of chalk at the bottom of the sea, which were afterwards to become our enormous chalk hills. Still backwards we must go through all that long period, and then through three others quite as long, with ever-changing scenes of life and climate and geography, till we find ourselves in those grand old forests whose trees and plants we now dig out as coal.