61 . 
urethral vail, are of efttodermal origin and are essentially unaf- 
y 
fected, and remain female in mode of development. 
The Phallus and External Genitalia. 
In females: 
The female external genitalia differ from those of the male 
in the perforation of the urogenital plate in early stages. This 
takes plaoe before the 2.8 cm. stage. At that time the position 
of the phallus is approximately the same in the two sexes, and both 
have genital swellings and teat primordia. In the female, as time 
goes on, the phallus becomes more recurved toward the anal opening, 
the vulva more open, and the perineum no wider relatively. The 
genital swellings in cattle, unlike those in the human, as described 
by McMurrick in his * Development of the Human Body", do not take 
part in the formation of the labia majora, as is shown by F. R. Lillie 
in his unpublished work on the homologies and fate of the external 
genitalia in oattle, but completely disappear in females at about 
10.0 cm. - 12.0 cm., and labia majors are absent in cattle. The 
lips of the genital plate form the genital folds and, finally, the 
labia minora. The plaoe of the absent labia majors is taken, in 
later stages, by the labia minora or nymphae, which grow out on the 
sides of the recurved phallus and approach its tip, finally over- 
lapping it in the older stages, though not by the 20.0 cm. stage. 
The tip of the phallus is cavernous and forms the glans clitoridis. 
In early stages the glans has an undercut groove in its dorsal part, 
filled with stratified epithelium. This disappears in later stages. 
The thick ventral wall of the vulva becomes cavernous, as the corpus 
caver no sum clitoridis, which is sinuous and does not have the great 
increase in lenght so characteristic of the male. The glans clito— 
ridis is knob-shaped at first, but by the 20.0 cm. stage it is pointed. 
The udder and teats develop and the genital swellings give rise to 
