Editing Digenea (section)

===Reproductive system===
The vast majority of digeneans are [[hermaphrodite]]s. This is likely to be an adaptation to low abundance within hosts, allowing the life cycle to continue when only one individual successfully infects the final host. [[Fertilisation]] is internal, with [[sperm]] being transferred via the [[cirrus (biology)|cirrus]] to the [[Laurer's Canal]] or [[genital|genital aperture]]. A key group of digeneans which are [[dioecious]] are the [[schistosoma|schistosomes]].
Asexual reproduction in the first larval stage is ubiquitous.

While the sexual formation of the digenean [[egg (biology)|eggs]] and asexual reproduction in the first [[larva]]l stage (miracidium) is widely reported, the [[developmental biology]] of the asexual stages remains a problem. [[Electron microscope|Electron microscopic]] studies have shown that the [[microscope|light microscopically]] visible germ balls consist of [[mitosis|mitotically]] dividing [[cell (biology)|cell]]s which give rise to [[embryo]]s and to a line of new [[germ cells]] that become included in these embryonic stages. Since the absence of [[meiosis|meiotic processes]] is not proven, the exact definition remains doubtful.

====Male organs====
[[Hermaphrodite|Protandry]] is the general rule among the Digenea. Usually two [[testes]] are present, but some flukes can have more than 100. Also present are [[vasa efferentia]], a [[vas deferens]], [[seminal vesicle]], [[ejaculatory duct]] and a cirrus (analogous to a penis) usually (but not always) enclosed in a cirrus sac.  The cirrus may or may not be covered in proteinaceous spines.  The exact conformation of these organs within the male terminal genitalia is taxonomically important at the familial and generic levels.

====Female organs====
Usually there is a single [[ovary]] with an [[oviduct]], a [[semen|seminal receptacle]], a pair of vitelline glands (involved in [[yolk]] and egg-shell production) with ducts, the ootype (a chamber where eggs are formed), a complex collection of glands cells called ''Mehlis’ gland'', which is believed to lubricate the uterus for egg passage.

In addition, some digeneans possess a canal called [[Laurer's Canal]], which leads from the oviduct to the dorsal surface of the body.  The function of this canal is debated, but it may be used for insemination in some species or for disposal of waste products from reproduction in other species.
Most trematodes possess an ovicapt, an enlarged portion of the oviduct where it joins the ovary. It probably controls the release of ova and spaces out their descent down the uterus.

The uterus typically opens into a common genital atrium that also received the distal male copulatory organ (cirrus) before immediately opening onto the outer surface of the worm.  The distal part of the uterus may be expanded into a metraterm, set off from the proximal uterus by a muscular sphincter, or  it may be lined with spines, as in the [[Monorchiidae]] and some other families.