CONTENTS. XV 



CHAPTER XV. PAGE 



THE ORGANS OF THE MIDDLE GERM-LAYER . . . .341 



I. THE DEVELOPMENT OF THE VOLUNTARY MUSCULATURE . . 342 



A. The Primitive Segments of the Trunk 342 



B. ,. Head-Segments 351 



II. THE DEVELOPMENT OF THE URINARY AND SEXUAL ORGANS . 353 



() The Pronephros and the Mesonephric Duct .... 353 



(b) Mesonephros (Wolffian Body) . . . . . .359 



(0) Metanephros (Kidney) . . . . , . .367 



(d) Miillerian Duct 369 



(<?) Germinal Epithelium . 374 



(/) Ovary 374 



(#) Testis 382 



(7<) ,, Metamorphosis of the Different Fundaments of the Uro- 



genital System into their Adult Condition ... . . 385 



A. In the Male (Descensus testiculorum) .... 387 



B. Female ( ovariorum) .... 393 



(1) The Development of the External Sexual Parts . . . 397 



III. THE DEVELOPMENT OF THE SUPRARENAL BODIES . , . 403 

 SUMMARY 405 



CHAPTER XVI. 

 THE ORGANS OF THE OUTER GERM-LAYER 416 



I. THE DEVELOPMENT OF THE NERVOUS SYSTEM . . . 416 



. 416 



. 418 



. 421 



. 427 



(2) fourth . 429 



(3) third 430 



(4) ., second 431 

 Development of the Pineal Gland (Epiphysis cerebri) 432 



., Hypophysis (Pituitary Body) . 436 



(5) Fore-Brain Vesicle . . . 439 

 J?. The Development of the Peripheral Nervous System . . 449 



(a) Spinal Ganglia 449 



(&) Peripheral Nerves . . . .452 

 (c) Sympathetic System .... 462 

 SUMMARY 463 



II. THE DEVELOPMENT OF THE SENSORY ORGANS .... 467 



A. The Development of the Eye 467 



() The Development of the Lens 471 



Vitreous Body . . . .474 

 Secondary Optic Cup and the 



Coats of the Eye . . .476 



(<T) Optic Nerve . . . .484 



(^) Accessory Apparatus of the Eye 486 



A. The Development of the Central Nervous System 

 (a) The Development of the Spinal Cord 

 (#) ,. ,. Brain . 



(1) Metamorphosis of the fifth Brain-Vesicle 



