x Contents 
PAGE 
Effects of Light on Growth : 3 3 : ‘i . . - . 261 
Growth toward the Light; Phototropism . . . « . . 265 
Influence of Gravity on Growth . ‘ ‘ , : F F . 266 
Effects of Electricity on Growth . ‘ ‘ 5 é - : . 267 
Pressure and Contact . ‘ - , . - 7 : : . 267 
The Formation of Galls : : 5 . . . . F + 268 
CHAPTER XVII 
GROWTH AND REGENERATION . «©. wee 2 
EXPERIMENTAL STUDIES IN GRAFTING 
CHAPTER XVIII 
EXPERIMENTS IN GRAFTING a . : , a - . . 285 
The Union of Different Regions . : : ‘ : « 285 
The Influence of the United Parts on Each Other: Formative Factors 289 
The Union of Parts of Different Species ; ji : P . 298 
Special Problems of Development : : : , . : - 301 
EXPERIMENTAL STUDIES OF THE INFLUENCE OF 
THE ENVIRONMENT ON THE LIFE-CYCLE 
CHAPTER XIX 
CHANGES IN THE LIFE-CYCLE AND CHANGES IN THE ENVIRONMENT + 309 
The Life Histories of Some Animals. . . , + 309 
Influence of Food on the Life-cycle of Lépidepters . 313 
Influence of the Environment on the Time of Ripening of the Sexual 
Organs. - : E ‘ 7 : . . : + 315 
CHAPTER XX 
ALTERNATION OF SEXUAL AND PARTHENOGENETIC FoRMS . J « 322 
Alternation of Generations in the Aphids and Phylloxerans . ‘ » 322 
CHAPTER XXI 
INFLUENCE OF EXTERNAL CONDITIONS ON THE LIFE-CYCLE OF THE 
LOWER CRUSTACEANS . . : - 7 , + 336 
CHAPTER XXII 
INFLUENCE OF EXTERNAL CONDITIONS ON THE LIFE-CYCLE OF THE Ro- 
TIFER, HYDATINA SENTA : . . . : é E » 346 
