Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free.This is an OCR edition with typos.Excerpt from book:LECTURE II. RELATIVE STANDING OB GRADATION OF THE ANIMAL KINGDOM. Ladies and Gentlemen : — I propose to-night to lay before you the subject of the relative standing or gradation of the animal kingdom. It is one which has long engaged the attention of naturalists. The favorite idea has been that all living beings form an unbroken natural chain from the lowest to the highest, or, as the phrase has been, "from the Monad to Man." This view has been greatly modified in the progress of investigation. It was, as it were, a theoretical view in the beginning, started by general impression, and not at once submitted to the severe scrutiny of a careful investigation; and when that was made, this idea was found not to be true in the form in which it had been stated. And yet the investigation has led to some interesting results; as, for instance, the discovery of the limits within which there is a gradation or relative rank, and beyond which there is not. This view of an unbroken continuity of the animal kingdom from the Monad to Man, was started before it became known that all animals are constructed upon four different plans, so that the differences of structure with reference to these plans was no obstacle to the formation of a supposed series or chain. The discovery of the four plans has in a great measure checked that theory, though at this moment it is reviving hi connection with questions which I shall hereafter consider, especially with reference to the question now so extensivelydiscussed among scientific men and philosophers, of the origin of species, of which I shall have something to say presently. But before considering that question, we should become familiar with the broad, comprehensive principles lying at the foundation of all natural science. I have already shown...