. Biology in America. Biology. 132 Biology in America western Kansas, which were once at the bottom of the old Cre- taceous Sea. Traces of teeth still occur in the embryos of some birds of the j)resent, a heritage from some ancestor of the distant past. While Icthyornis still had teeth, it had pro- gressed much further along the path of avian development than Archffiopteryx in the structure of the hand. Nature in her experiments is prodigal in the production of variations, most of which she will never use in the development of new species; but once she is on the track of a useful variation she
. Biology in America. Biology. 132 Biology in America western Kansas, which were once at the bottom of the old Cre- taceous Sea. Traces of teeth still occur in the embryos of some birds of the j)resent, a heritage from some ancestor of the distant past. While Icthyornis still had teeth, it had pro- gressed much further along the path of avian development than Archffiopteryx in the structure of the hand. Nature in her experiments is prodigal in the production of variations, most of which she will never use in the development of new species; but once she is on the track of a useful variation she becomes a strict conservationist and wastes no energy in the. Hesperornis extinct diving bird with teeth, an inhabitant of the great Creta- sea wliif h once covered our Great Plains. From Lucas, '' Animals Au ceous of the Past.'' Courtesy of the U. -b'. yatiuiuil Museum. maintenance of useless parts. So in the hand of the modern bird and in Icthyornis as well, we find one of the fingers being greatly strengthened for the support of the wing feathers, and the others correspondingly reduced. The typical reptile has five fingers, which in the modern bird are reduced to one plus two rudiments, while Archa?opteryx had dropped only two of his digits and still remained in possession of the claws on his wings wliich the modern bird has dispensed with as entirely out of date. There is however one conservative member of the class who still retains a reminder of his rep- tilian past in the form of a claw at the angle of the wing,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Young, R. T. (Robert Thompson), b. 1874. Boston, R. G. Badger
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