(1.) To form a just estimate of the relative position of any science at a given period, it is necessary that the prominent events in its history be rightly understood. It seems, therefore, expedient to commence this discourse with a slight sketch of the rise and progress of zoological science; or, more properly, of the progressive discovery of the forms, structures, and habits belonging to the animal world; a world replete with such an infinity of beings, each possessing so many peculiarities of habit and economy, that, notwithstanding the united efforts of human research for thousands of years, there is not one of them whose history, as yet, can be pronounced complete.

(2.) The vast and diversified field of enquiry over which zoology extends, and the many distinct portions into which it is now distributed, render it extremely difficult to embrace the whole in one general exposition. For it has happened, that at one period of time while our knowledge has made gigantic progress in one department, it has been stationary, or even retrograde, in others; and at another epoch we find that original research has been abandoned, and the technicalities of system and nomenclature alone regarded. To meet the first difficulty, and to preserve, nevertheless, a connected narrative, it seems advisable to treat the subject historically; and pre-supposing certain epochs in this science, to detail the peculiar characteristics of each.