CONTENTS. XV 



CHAPTER XV. PAGE 



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

 L 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 



(c) Metanephros (Kidney) ....... 367 



(d) Miillerian Duct 369 



(e) Germinal Epithelium . 374 



(/) Ovary 374 



(#) Testis 382 



(/*) ,, 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 

 (i) 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 



A. The Development of the Central Nervous System . . . 416 

 (a) The Development of the Spinal Cord . . . .418 

 (&) Brain 421 



(1) Metamorphosis of the fifth Brain-Vesicle . . . 427 



(2) v fourth 429 



(3) third 430 



(4) ., second 431 

 Development of the Pineal Gland (Epiphysis cerebri) 432 



Hypophysis (Pituitarj**Body) . 436 



(5) Fore-Brain Vesicle . . .439 

 JB. The Development of the Peripheral Nervous System . . 449 



O) Spinal Ganglia 449 



(ft) Peripheral Nerves . . . .452 



(0) Sympathetic System .... 462 



SUMMARY 463 



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



A. The Development of the Eye . . . . . .467 



O) The Development of the Lens 471 



Vitreous Body . . . .474 

 ,, Secondary Optic Cup and the 



Coats of the Eye . . .476 



(d-) ,, Optic Nerve . . . .484 



(e) Accessory Apparatus of the Eye 486 



