CONTENTS. XV 



CHAPTEE XV. PAGE 



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



I. THE DEVELOPMENT OF THE VOLUNTAEY MUSCULATURE . . 342 



-i. The Primitive Segments of the Trunk , 342 



S. Head-Segments 351 



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



(a) The Pronephros and the Mesonephric Duct , 353 



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



(c) Metanephros (Kidney) 367 



(rf) 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 testiculomm) .... 387 



B. Female ( ovariorum) .... 393 

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



III. THE DEVELOPMENT OP 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 

 (V) Brain 421 



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



(2) fourth ., 429 



(3) third 430 



(4) ., ,, second . . . 431 

 Development of the Pineal Gland (Epiphysis cerebri) 432 



., Hypophysis (Pituitaiy Body) . 436 



(5) ,, Fore-Brain Vesicle . . .439 



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



(a) Spinal Ganglia , 449 



(J) Peripheral Nerves .... 452 



(c) Sympathetic System .... 462 



SUMMARY 463 



II. THE DEVELOPMENT OP THE SENSORY ORGANS 4C7 



A. The Development of the Eye 467 



(a) The Development of the Lens . . . . . . 471 



(&) ,, Vitreous Body . . . .474 



(c) Secondary Optic Cup and the 



Coats of the Eye . . .476 

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



(e) Accessory Apparatus of the Eye 486 



