Page:Popular Science Monthly Volume 73.djvu/568

564 animal such an advantage that it is practically free from all its enemies and in this dominant or protected condition it may become over nourished and the originally useful structures may t continue to grow by a kind of inertia or momentum until they become greatly exaggerated masses of flesh or inordinately developed spines, horns, feathers, etc. Such a development seems to have occurred once and again in the history of the world, and the most bizarre types of life owe something of their condition, at least, to tins principle. The late Professor Beecher, of Yale, has shown that there is a decided tendency, both in plants and in animals, for a species that is nearing the point of its extinction to develop a spiny or horny habit, covering itself with all sorts of excrescences, seemingly in an unregulated effort to find some condition which will prolong its existence. It is certain that these reptiles, dominant as they were, were rapidly completing their allotted span and as the end approached the spines grew ever heavier and heavier, until it seems plausible to suggest that they became at last a great drain on the animal's powers of nutrition and hastened in no slight degree the end.

 Naosaurus, showing the peculiar dentition.