published in book form in 1843 and in 1860-68—the former a volume on the invertebrata, and the latter, in three volumes, on the vertebrata; and in 1855 another series of lectures on the comparative anatomy and physiology of the invertebrate animals was published in book form, the volume occupying 689 pages of print, with 235 illustrations. In the concluding lecture Owen says:—
The invertebrated classes include the most numerous and diversified forms of the Animal Kingdom. At the very beginning of our inquiries into their vital powers and acts we are impressed with their important relations to the maintenance of life and organization on this planet, and their influence in purifying the sea and augmenting and enriching the land—relations of which the physiologist conversant only with the vertebrated animals must have remained ignorant.
These lectures were welcomed both in England and on the Continent; and in his work on the Archetype and Homologies of the Vertebrate Skeleton he made at the time a contribution of a high order to what may be termed the philosophy of natural history, showing how closely the bones, especially in the head, of vertebrate animals conform to a general type; but the ideas expressed in this work limited his vision. This was a misfortune, as his theory has been altered by the subsequent work of embryologists.
In his work on the Archetype he dissented from the philosophy of Cuvier, and was inclined to that of Oken and Geoffroy Saint-Hilaire. In matters of morphological speculation Owen passed from the school of Cuvier into
