[1] This is true if a strictly logical treatment of the subject is held to. As a matter of fact, it is often of advantage to begin with, or at least to take up from the beginning in connection with the indoor work, some field-work, such as the collecting and classifying of insects and the observation of their metamorphosis. As most schools begin work in the fall, advantage must be taken of the favorable opportunities for field-work at the beginning of the year. These opportunities are of course much less favorable in the winter. [2] The classification of animals used in this book is that adopted in Parker and Haswell's "Text-book of Zoology" (2 vols., 1897, Macmillan Co.). Exception is made in the case of the worms, which are considered as a single branch, Vermes, instead of as several distinct branches. CONTENTS PART I STRUCTURE, FUNCTIONS, AND DEVELOPMENT OF ANIMALS I.--THE STUDY OF ANIMALS AND THEIR LIFE. Our familiar knowledge of animals and their life, 1.--Zoology and its divisions, 2.--A first course in Zoology, 3. II.--THE GARDEN TOAD (BUFO LENTIGINOSUS). [Laboratory exercise], 5.--External structure, 5.--Internal structure, 7. III.--THE STRUCTURE AND FUNCTIONS OF THE ANIMAL BODY. Organs and functions, 14.--The animal body a machine, 14.--The essential functions or life-processes, 15. IV.--THE CRAYFISH (CAMBARUS SP.). [Laboratory exercise], 17.--External structure, 17.--Internal structure, 21. V.--THE MODIFICATION OF ORGANS AND FUNCTIONS. Difference between crayfish and toad, 26.--Resemblances between crayfish and toad, 27.--Modification of functions and structure to fit the animal to the special conditions of its life, 29.--Vertebrate and invertebrate, 30. VI.--AMŒBA AND PARAMŒCIUM. [Laboratory exercise], 31.--Amœba, 31.--The slipper-animalcule (PARAMŒCIUM SP.), 34. VII.--THE SINGLE-CELLED ANIMAL BODY; PROTOPLASM AND THE CELL. The single-celled animal body, 36.--The cell, 37.--Protoplasm, 39. VIII.-CELLULAR STRUCTURE OF THE TOAD (OR FROG). [Laboratory exercise], 40.--The blood, 40.--The skin, 40.--The liver, 41.--The muscles, 41. IX.--THE MANY-CELLED ANIMAL BODY; DIFFERENTIATION OF THE CELL. The many-celled animal body, 43.--Differentiation of the cell, 43. X.--HYDRA. [Laboratory exercise], 46. XI.--THE SIMPLEST MANY-CELLED ANIMALS. Cell-differentiation and body-organization in Hydra, 52.--Degrees in cell-differentiation and body-organization, 54. XII.--DEVELOPMENT OF THE TOAD. [Field and laboratory exercise], 55. XIII.--MULTIPLICATION AND DEVELOPMENT.