4 22 



THE EVOLUTION OF MAN. 



anua Even before the appearance of this partition, in the 

 Pouched Animals (Marsupialia) and Placental Animals, a 

 conical papilla the sexual protuberance (phallus, Fig. 329, 

 A, e, B, e) rises on the anterior part of the circumference of 



P. B. 



FIG. 329. External sexual organs of the human embryo : A, neutral 

 germ (in the eighth week ; twice the natural size ; with cloaca) ; B, neutral 

 germ (in the ninth week; twice the natural size; anus distinct from the 

 urogenital opening) ; C, female germ in the eleventh week ; D, male germ 

 in the fourteenth week ; e, sexual protuberance (phallus') ; /, sexual furrow ; 

 hi, sexual folds ; r, Eaphe (point of union of the penis and scrotum) ; 

 a, anus ; ug, urinary sexual opening ; n, navel-cord ; s, tail. (After Ecker.) 

 Cf. Table XLIV., p. 431. 



the cloaca-opening. The apex of this is swollen into a knob 

 (the "acorn," glans). On the under side appears a furrow 

 (sulcus genitalis, /), and on each side of the latter a skin- 

 fold, or sexual fold (M). The phallus is especially the organ 

 of the " sexual sense," and over it are distributed the sexual 



