mistakable manner the thoroughly intermediate' nature of this animal. Its upper jaw bore two small conical teeth; the breast-bone is reduced to zero;' and, whilst its arm-bones 'present no features peculiar to reptiles or to birds,' its hand1 can be compared neither to that of a bird, nor to that of a pterodactyl,2 but to that of a three-toed lizard. 'If the feathers had not been preserved,' says Vogt, 'no one could ever have suspected, that, from the examination of the skeleton alone of archaeopteryx, this animal was furnished with wings when alive.' Head, neck, chest and ribs, tail, shoulder-girdle, and arm or wing, are all built on a reptilian type; the haunch is more reptilian than bird-like; but the hind limbs are those of a bird. The reptile characters unquestionably predominate in the skeleton, just as the bird characters come to the front in the feathers. "Professor Vogt strenuously asserts, that a study of archeopteryx shows that it is neither bird nor reptile, but that it is a decided 'link' between the two classes." 3 The following figure may give an approximate idea of how the living Archæopteryx looked. Many other instances might be given of animals more or less perfectly intermediate between birds and reptiles, such as the birds found in Kansas rocks of the mesozoic era by Professor O. C. Marsh. These birds had double concave vertebræ (as reptiles have), and forty or more 1 Or end of the wing. 2 A kind of fossil flying-lizard. 8 Wilson's Chapters on Evolution, p. 159. teeth in the lower jaw alone. Again: the earliest fishes were in some respects intermediate between fishes and reptiles; so that one could hardly look at the figure of Pterichthys already given, without being forcibly reminded of such reptiles as the marine turtles. Others of the earliest fossil fishes with strongly reptilian char acteristics closely resembled their degenerate descendants of the present day, the gar-pikes of our Western lakes and rivers. It is, says the great zoologist Rütimeyer, only their retreat into fresh water that has saved these gar-pikes from the fate of extinction that has befallen their marine ancestors of palæozoic seas.1 1 That is, by becoming acclimated to fresh water, they have escaped the far more severe struggle for existence that goes on in the sea. The great sea-lizards of the reptilian age, one of which is figured below, seem to have had shark-like intestines, and, from this fact and some others, to have been related to both lizards and fishes. The early nerve-winged insects, which are closely related to the modern dragonflies, had certain characteristics of the grasshopper of the present day. How can facts of this kind be more naturally interpreted than by considering the modern less comprehensive types to be descended from the elder more comprehensive one, which by variation has given rise to two or more later groups? It is true there are many exceptions to the general rule, that the first introduced members of each type are its lowest representatives. There is, however, in many of these cases, reason to suppose that the exception is only apparent, and would disappear if the life-history of the earth were more perfectly known; but there are others which are probably not to be explained by any knowledge which the paleontologist can acquire. Important and puzzling as they may be, these exceptions are not sufficient to prevent the general conclusion, that the law of life has been progress, by modified descent, from lower to higher forms. Illustrations of this law additional to those already mentioned may be found in great numbers in any work in which paleontology is at all fully treated.1 From the protozoans of eozoic time to the invertebrate sub-kingdoms of the lower silurian; from these to the fishes of upper silurian time, then to the amphibians and the true reptiles of the carboniferous, to the first birds of the reptilian, and the mammals of the same age; from these lowly quadrupeds up to man, — how closely this ascending scale of being corresponds to what the development theory would lead us to expect! In the series of fossil plants, the general law of progress is exemplified; since the earliest 1 Nicholson's Ancient Life-History of the Earth is one of the most compact and readabie elementary works. found are algæ, and it is only at a very late period that dicotyledons appear. That the law cannot among plants be verified nearly as much in detail as among animals is no doubt due in part, if not entirely, to the fact that we have a far less perfect paleontological record of plants than of animals; for plants have no parts which are as durable as the bones and teeth of vertebrates, the shells of mollusks, or the limy skeletons of corals. Then, too, if we except the seaweeds (which are preserved with difficulty), the greater part of the world's flora is terrestrial. On the other hand, the greater bulk of its fauna is now aquatic, and this predominance of aquatic animals was much more pronounced in the earlier geological ages; so that the chances are far more. in favor of a comparatively full representation of extinct forms of animal than of plant life. Lichens and toadstools are of so low organization, that they might be expected to appear very early among fossil plants. It is not strange, however, that their fossils are late to appear, and very rare; since their lack of woody fibre, and their terrestrial habits, must have rendered it extremely difficnlt for their remains to be preserved. In the cycads (one of which is here figured) |