CONTENTS XI 



C. Cleavage and morphochoretic pattern 325 



D. Kinetic and causative aspects of intrinsic morphochoresis 341 



(a) The factors at work, 341 - (b) Enumeration of the problems, 342 - 



(c) The localisation of the blastopore in Anamniots. An operative approach, 

 342 - (d) Interpretation of kinematics in amniots, 347 - (e) Some bio- 

 chemical information, 348 - (f) Modifying intrinsic morphochoresis by 

 operative and biochemical means, 350 - (g) Intradermic inductions, 351 - 



E. Mechanisms of intrinsic morphochoresis. A discussion 354 



III. Neurogenic Induction, the Main Aspect of Extrinsic Morphochoresis (with 

 some data on non-neurogenic inductions) 357 



A. Observations 358 



B. Experimental data relative to primary induction 366 



(a) Operations on the whole embryo, 366 - (b) Explantations of un- 

 modified territories, 396 - 



C. Experimental modifications of morphochoresis 411 



(a) Physical means, 411 - (b) Biochemical modification of inductors and 

 reactors, 419 - 



D. Xeno-inductions 427 



(a) Fresh foreign tissues, 427 - (b) Killed foreign tissues, 428 - (c) Regional 

 influence of the host, 431 - (d) First approaches to the nature of the xeno- 

 inductors, 431 - (e) Fractionation of the xeno-inductors, 433 - (f) Inter- 

 pretative remarks, 443 - 



E. Secondary and minor inductions 448 



(a) The cephalic placodes, 449 - (b) Neural crest and derivatives, 454 - 



(c) Limb buds, 456 - (d) Some epiblast derivatives, 459 -(e) The induction 

 of cartilages and somites, 461 - (f) Other in vitro inductions, 463 - 

 (g) Gonadic inductions, 466 - 



F. General remarks on induction 467 



(a) About definition, 468 - (b) On the evolution of inductive processes, 



468 - (c) On the appreciation of the data, 469 - (d) On the morphogenetic 

 effects of induction, 469 - (e) On the nature of the inducing agents, 474 - 

 (f ) On the intimate changes in the reactor, 479 - 



IV. Final Considerations 479 



Literature 483 



Chapter 5. Molecular Mechanisms of Differentiation. An Inquiry into the 



Protein Forming System of Developing Cells, by Heinz Herrmann . . . 495 



I. Introduction 495 



II. The Utilization of Protein Precursors in the Differentiating Cell . . . . 497 

 (a) Precursors larger than amino acids, 497 - (b) Amino acids as precursors, 

 498 - (c) Pathways of precursor utilization, 505 - 



III. The Protein Forming System (PFS) of Differentiated and Embryonic Cells . 507 

 (a) Nucleic acids as components of the PFS, 509 - (b) Structural aspects of 



the PFS : Protein formation in microsomes and mitochondria, 5 1 2 - (c) Nucleo- 

 cytoplasmic interactions related to protein formation, 514 - 



IV. Regulating Factors of the PFS During Development 518 



(a) Apparent qualitative changes in the PFS (Induction), 519 - (b) Apparent 

 quantitative aspects of protein formation in embryonic cells, 522 - (c) The 

 relation of proliferation and differentiation, 523 - 



V. Conclusions : The Convergence of Concepts 530 



Literature 539 



