<Li> The corpora cavernosa of each of the penis and clitoris and of the urethra arise from the mesodermal tissue in the phallus; they are at first dense structures, but later vascular spaces appear in them, and they gradually become cavernous . </Li> <Li> The prepuce in both sexes is formed by the growth of a solid plate of ectoderm into the superficial part of the phallus; on coronal section this plate presents the shape of a horseshoe . By the breaking down of its more centrally situated cells the plate is split into two lamellæ . Thus, a cutaneous fold, the prepuce, is liberated and forms a hood over the glans . </Li> <P> In the female, a deep groove forms around the phallus . The sides of it grow dorsalward as the labioscrotal folds, which ultimately form the labia majora in females . The labia minora, in contrast, arise by the continued growth of the lips of the groove on the under surface of the phallus; the remainder of the phallus forms the clitoral glans . </P> <P> In the male the pelvic portion of the cloaca undergoes much greater development, pushing before it the phallic portion . </P>

When do male and female reproductive systems develop