THE URINOGENITAL SYSTEM 189 
In the wholly vestigial condition the mesonephros is not infrequently 
the seat of origin of pathological affections (formation of cysts). 
The vestigial portions of the mesonephros in men are 
the paradidymis, Giraldé’s organ, and the stalked hydatids of 
Morgagni; in women it gives rise to the greater part of the 
parovarium and the whole of the paroophoron. Further, in 
women, the last vestiges of its duct are found, either confined to 
the region of the parovarium, or, where suppression is least 
marked, in the form of “Gartner’s canal” which reaches the vagina. 
MULLERIAN Duct 
Van Wijhe, believing that the ancestors of the vertebrate were 
hermaphrodite, has argued that the first appearance of the Miillerian 
duct probably dates back to a period in the evolution of the phylum 
when, as a means of preventing self-fertilisation, there were 
distinct ducts for the transmission of the sperm and the ova. Be 
this as it may, the secondary nature of the Miillerian duct is 
shown by its comparatively late development in the individual. 
It originates in the Amniota by evagination of the ccelomic 
epithelium, to form a structure which, becoming constricted off 
into a tube, gradually elongates in a caudal direction to reach 
the cloaca. 
In the male, the duct of the mesonephros, and in the female, 
as is well known, the whole of the Miillerian duct, forms the 
adult genital duct (cf. Fig. 103). In the male the greater part 
of the Miillerian duct degenerates or entirely disappears, thus losing 
nearly all physiological significance. Its proximal vestige becomes 
in Man the unstalked hydatid of Morgagni, a small appendage of 
the testis; its distal end, however, is believed to unite with that 
of its fellow of the opposite side to form a vesicle, the “ uterus 
masculinus,’ which becomes embedded in the prostate, and later 
opens, conjointly with the vasa deferentia, into the urinogenital 
sinus (urethra). 
1 [The term ‘‘uterus masculinus” is applied, by analogy, to a somewhat 
similarly placed median vesicle, opening into the prostatic portion of the urethra 
in other Mammals. One well-known case is that of the common Rabbit. The 
so-called ‘‘uterus masculinus” of that animal certainly does superficially resemble 
that of Man, but the two differ fundamentally in their relationships to the vasa 
differentia, 7.c. in Man the bases of these pass behind the vesicle and open at its 
sides, while in the Rabbit they pass in front of it and open within its anterior lip. 
Kolliker from the study of its development, has claimed for the so-called ‘‘ uterus 
masculinus” of the Rabbit) (Hntwicklungsgesch. d. Menschen n. d. hihern Thiere, 
