The distinctive character of this work consists in the treatment of the whole Animal Kingdom as a unit; in the comparative study of the development and variations of organs and their functions, from the simplest to the most complex state; in withholding Systematic Zoology until the student has mastered those structural affinities upon which true classification is founded; and in being fitted for High Schools and Mixed Schools by its language and illustrations, yet going far enough to constitute a complete grammar of the science for the under-graduate course of any College. It is designed solely as a manual for instruction.