CONTENTS IX 



Xm. GROWTH 279 



1. Overall groii'th 279 



2. The relative growth of parts 287 



3. Growth gradients and transformations of shape 290 



XIV. REGENERATION 302 



1. The origin of regeneration cells and their potentialities 303 



2. Field action in regeneration 



a. Coelenterates 309 



b. Flat worms 3I7 



c. Amphibia 321 



PART TWO 



THE FUNDAMENTAL MECHANISMS OF 

 DEVELOPMENT 



XV. THE ROLE OF THE GENES IN THE EPIGENETIC 329 



SYSTEM 



1. Developmental pathways and their genetic control 329 



2. Primary and secondary effects of genes 341 



XVI. THE ACTIVATION OF THE GENES BY THE 348 



CYTOPLASM 



1. The effects of the cytoplasm on the nucleus 351 



2. Effects on chromosomes and genes 355 



3. Complete or partial inactivation of genes? 361 



4. The mechanism of gene activation or inhibition • 364 



XVII. THE SYNTHESIS OF NEW SUBSTANCES 3^7 



1. The parts of the cell 367 



2. Arguing from the gene to the substance 371 



3. Arguing from the substance to the gene 376 



4. Genes and enzymes 378 



5. The synthesis of proteins , 381 



XVIII. PLASMAGENES 3^7 



1. Exogenous plasmagenes 389 



2. True plasmagenes 392 



3. Visible cytoplasmic particles with genetic continuity 393 



4. Gene-initiated plasmagenes 39^ 



5. The role of plasmagenes in differentiation 401 



