CONTENTS. XV 



CHAPTER XV. . PAGB 



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



I. THE DEVELOPMENT OP THE VOLUNTARY MUSCULATURE . . 342 



.4. The Primitive Segments of the Trunk .' ' .; V .342 

 S. Head-Segments . .."-.'.'. . .' . .351 



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



O) 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 



(h) Metamorphosis of the Different Fundaments of the Uro- 



genital System into their Adult Condition . . . .385 



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



S. 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 

 (Z>) 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 (Pituitary Body) . 436 



(5) Fore-Brain Vesicle . . .439 



B. 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 



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



(&) Vitreous Body . . . .474 



(c) Secondary Optic Cup and the 



Coats of the Eye . . .476 



(<0 Optic Nerve . . . . 484 



(f> Accessory Apparatus of the Eye 486 



