HORMONES IN DIFFERENTIATION OF SEX 



121 



Fig. 2.27. The effects of castration on the development of the prostatic glands in the rab- 

 bit. A. The sinus region in a male fetus, aged about 27 days, castrated before the 20th day 

 of gestation; above is the canal of the urinogenital sinus, below it the dark, bilobed struc- 

 ture represents the vaginal cord as it unites with the wall of the sinus. No sign of prostatic 

 buds is seen. B. The sinus region in a young male of the same age castrated at about 21 

 days (20 days, 20 hours). Two large prostatic buds are seen ventral to the vaginal cord 

 which were present at the time of castration. No further development has occurred. C. The 

 sinus region in a male fetus of 28 days, castrated at the age of 23 days. Castration at this 

 age is followed by essentially normal development. (From A. Jost, Arch. Anat. microscop. et 

 Morphol. exper., 36, 271-315, 1947.) 



Fig. 2 2S Hi-told.i In k lu ( - be twcin noimal h i i i i I , i i \ternal 



genitalia {B) m i.ihlut htu^i^ aitcM -e\ual diffeientiation Mk uiinoj-nut il uu itu^ i-^ larger 

 in the fem<ile, and is onh p.uth >uiioundcd b^ the pieputial fold, ■wliith maik'- off the glans 

 clitoridis from the surrounding tissues. In the male the urethral cleft is narrower and com- 

 pletely enclosed within the preputial fold. The paired erectile bodies are seen above the 

 urethral cleft. Castration at an early stage alwaj^s results in genitalia of female type (A) re- 

 gardless of the sex of the castrated embrvo. (From A. Jost, Arch. Anat. microscop. et Mor- 

 phol. exper., 36, 271-315, 1947.) 



Altogether, the evidence clearly indicates 

 that the male hormone is the essential de- 

 termining factor in the survival and sexual 

 differentiation of the male sex ducts and 

 seminal vesicles. Notwithstanding the minor 

 exceptions noted above, the female hor- 

 mone evidently has little role. The reason 

 for the insensitivity of the Wolffian ducts 

 to the female hormone may possibly be 

 found in their long phylogenetic history as 

 nephric ducts in both sexes, in which ca- 

 pacity they must be retained in some groups 

 beyond the period of sex differentiation or 

 even permanently. 



B. DERIVATIVES OF THE CLOACA AND 

 URINOGENITAL SINUS 



Sexual dimorphism of the amphibian clo- 

 aca chiefly takes the form of special cloacal 

 glands which in males become highly de- 

 veloped at the breeding season, causing the 

 prominent swelling of the cloacal region so 

 conspicuous in males. In the females of vari- 

 ous species they may be absent, present in a 

 rudimentary state, or in some cases dif- 

 ferently specialized (Noble, 1931). For their 

 development and maintenance these glands 

 depend almost entirely on the testis. After 

 experimental transformation of sex, the sub- 

 sequent differentiation of the cloacal glands 



