LIST OF ILLUSTRATIONS xx iii 



416. Epithelial cells from the bladder of the rabbit . . . .452 



417. Transection of the female urethra 453 



418. Diagram of a male genitalia (adapted from Merkel) . . . 455 



419. Diagram of female internal genitalia 456 



420. Diagrams illustrating the metamorphoses of the indifferent urogeni- 



tal system into the male and female systems . . . ~.~457 

 421. Diagrams illustrating the process of maturation in the male and 



female gametes 462 



422. Primary spermatocyte of a grasshopper, Hippiscus tuberculatus, 

 showing the compact accessory chromosome among the paler 



mossy prophase euchromosomes, and the idiosome . . . 464 



423. Chromosome groups of Schistocerca damnifica .... 473 



424. Diagram illustrating the behavior of the chromosomes during the 



first and second maturation divisions ..... 474 



425. The testicle with its system of efferent passages .... 480 



426. Seminal tubule of a man in transection ..... 481 



427. Sertoli cells of the human testis ...... 482 



428. Portion of a transection of a seminiferous tubule from the human 



testis, illustrating the various stages in spermatogenesis . . 483 

 429. Successive stages in the metamorphosis of the spermatid into the 



spermatozoon ......... 484 



430. Diagram of human spermatozoon . . . . . 485 



431. Spermatozoa of various animals . . . . . . 486 



432. Spermatozoa from the semen of man ..... 487 



433 . A group of interstitial cells from the testis of a thirty-five year old negro 488 



434. Interstitial cells from the human testis 489 



435. A small portion of the wall of an efferent ductule of the testicle . 491 

 436. Efferent ductules of the rabbit's epididymis .... 491 

 437. Several coils of the rabbit's epididymis in transection . . . 492 

 438. Transection of the ductus deferens of a dog .... 494 

 439. From a section through the wall of a seminal vesicle of man . 495 

 440. Model of a reconstructed prostate gland of man .... 496 

 441. Several alveoli of the human prostate gland, seen in section . 498 

 442. Portion of prostate gland of an old man, showing the prostatic con- 

 cretions .......... 499 



443. Prostatic genital corpuscles 500 



444. Reconstruction of a bulbo-urethral (Cowper's) gland of man . 501 



445. From a section of the bulbo-urethral (Cowper's) gland of man . 501 



446. Transection of a child's penis, just back of the glans . . . 503 



447. Helicine artery in section, from the urethral bulb of man . . 504 



448. The erectile tissue of the penis 505 



449. Section of ovary of adult cat, showing five vesicular (Graafian) folli- 

 cles, four with the cumulus oophorus and the enclosed ovum . 508 



