CONTENTS 



*XX. Some forms of plant life, with special reference to 



nutrition and reproduction . . . . .111 

 * XXI. A study of the ways plants are modified by their sur- 

 roundings ..,.>. * . . 110 



THE BIOLOGICAL INTERRELATIONS OF PLANTS AND 

 ANIMALS 



XXII. Some relations of fungi to man . . ? <- . 123 



XXIII. A study of bacteria and of some of their relations to 



man . . . . -. V - ; . - . ' :.. . 125 



XXIV. A study of some biological relations of plants and 



animals ., - ,* . .. '. . . 133 



THE PHYSIOLOGICAL UNIT AND DIVISION OF LABOR 



XXV. To study a one-celled animal, in order to understand 



better the unit of animal structures . . . 140 

 XXVI. An introductory study of many-celled animals (Met- 



azoa) . . . ... . , ;' - ' . 143 



SOME REACTIONS AND ADAPTATIONS AMONG ANIMALS 



* XXVII. The relations of the earthworm to its surroundings . 151 

 XXVIII. A study of some animal associations .... 153 

 *XXIX. A study of the idea of adaptations as shown in the 



crayfish .... ^. . . . .162 



THE MOST SUCCESSFUL ANIMALS, INSECTS, AND 

 THEIR RELATION TO MAN 



XXX. A study of some animal likenesses and differences, and 



the classification of insects 170 



XXXI. How insects became winners in life's race . . . 179 



XXXII. Some relations of insects to man 182 



THE BIOLOGICAL RELATIONS OF SOME AQUATIC FORMS 



OF LIFE 



XXXIII. A study of mollusks with special reference to their 



economic importance . . . .194 



