CONTENTS. XV 



CHAPTER XV. PACE 



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 



(ft) Mesonephros (Wolffian Body) 359 



(tf) Metanephros (Kidney) 367 



(d) Mullerian Duct 369 



(<?) ,, Germinal Epithelium . 374 



(/) Ovary . . 374 



( ff ) Testis 382 



(/<) ,, Metamorphosis of the Different Fundaments of the Urn- 

 genital System into their Adult Condition .... 385 



A. In the Male (Desecnsus 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 



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

 (ft) Brain 421 



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



(2) fourth ,. 429 



(3) third : , 430 



(4) * ., second n 431 

 Development of the Pineal Gland (Epiphysis cerebri) 432 



Hypophysis (Pituitary Body) . 436 



(5) Fore-Brain Vesicle . . .439 



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



() ,. Spinal Ganglia 449 



(ft) ,. Peripheral Nerves .... 452 



(e) ,. 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 



(ft) .,. * Vitreous Body . . . .474 



(c) ,, Secondary Optic Cup and the 



Coats of the Eye . . . 476 



(rf) ., ., Optic Nerve . . . .484 



(tf) ,. ., ,, Accessory Apparatus of the Eye 486 



