CHAP. XLII.] OF ORGANS OF GENERATION. 611 



gated by Miiller. From this canal, in the male, is formed the 

 Weberian organ, or uterus masculinus, while in the female it gives 

 origin to the uterus and vagina. 



The upper part of the excretory duct of the Wolffian bodies in 

 the male becomes much modified in character, and is ultimately 

 converted into the epididymis, whilst the lower portion becomes 

 the vas deferens. 



The lower part of the urino- genital canal, which becomes con- 

 verted into the external organs of generation, for some time pre- 

 sents a cleft or fissure on its inferior surface, which in male 

 reptiles and birds remains open thoughout life, but in mammalia 

 becomes converted into a canal, which extends to the tip of the 

 penis in the male, or along the under surface of the clitoris in the 

 female. Sometimes, however, a portion remains open, and the wall 

 of the urethra is deficient in its anterior part below, when the 

 congenital deformity known as hypospadias results. The folds of 

 skin which bound the furrow ultimately become converted into the 

 scrotum of the male, or labia of the female. The testicles descend 

 into the cavity of the scrotum about the eighth month, but not 

 unfrequently are retained within the abdominal cavity. 



The authors would refer particularly to the following works with reference 

 to the subjects discussed in the present chapter : Miiller's Physiology ; 

 Kathke, Beitrage zur Geschichte der Thierwelt ; Valentin, Entwickelungs- 

 Geschichte ; Dr. Handfield Jones on the Structure and Development of the 

 Liver, Phil. Trans., 1849 ; Victor Carus' System der Thierischen Morphologic ; 

 Eeichert, das Entwickelungsleben im Wirbelthier-Reich ; Mr. Marshall's 

 paper On the development of the great anterior veins in man and mammalia, 

 Phil. Trans., 1850 ; Mr. Gray's papers on the development of the ductless 

 glands in the chick, Phil. Trans., 1852 ; and his paper on the development of 

 the retina and optic nerve, and of the membranous labyrinth and auditory 

 nerve, Phil. Trans., 1850. 



