TABLE OF CONTENTS xv 



LESSON XIII. 



PAGE 



SPECIES AND THEIR ORIGIN : THE PRINCIPLES OF CLASSIFICA- 

 TION 137 



LESSON XIV. 



THE FORAMINIFERA 148 



THE RADIOLARIA 152 



THE DIATOMACE^S 155 



LESSON XV. 



MUCOR 158 



LESSON XVI. 



VAUCHERIA 169 



CAULERPA 175 



LESSON XVII. 



THE DISTINCTIVE CHARACTERS OF ANIMALS AND PLANTS . . 176 



LESSON XVIII. 



PENICILLIUM 184 



AGARICUS IQI 



LESSON XIX. 



SPIROGYRA 194 



LESSON XX. 



MONOSTROMA 2OI 



ULVA 203 



NITELLA 203 



