Turbellarians
In planarians reproductive system contains two testicles, consisting of seed bags with seminiferous tubules. The paired vas efferens fall into ejaculatory canal, penetrating copulatory organ - the penis analogue, which opens into genital atrium - dermal invagination, where the opening and female ducts. There are paired ovaries and oviducts departing from them. On the oviducts are numerous glands - vitellaria producing yolk cells filled with yolk needed to supply the developing eggs. Oviducts empty into the vagina, which opens a hole in the genital cloaca.
Most tubellyary is cross-fertilization, in which sexual partners pass each other male gonads, that is by turns appear as partners of a male and a female. Copulatory organ is usually introduces the semen directly into the genital atrium, some in sexual cesspool of a small protuberance - copulatory pouch, which receives the resulting seed. Possible and the previously mentioned method in which the copulatory organ simply pierces the wall of a sexual partner and the sperm is injected directly into his body, after which the sperm themselves are moving in the direction of the eggs. But in any case, the Turbellaria is internal fertilization. The fertilized egg yolk together with a group of cells is covered by a protective shell, and forms a complex egg, which is characteristic for the majority of flatworms.
The development of most Turbellaria direct, that is out of the egg body, similar to the adult animal, but some marine tubellyary development is a metamorphosis. At the same time the egg comes out quite unlike the adult worm larva myullerovskaya, which is covered with cilia, by which it floats. Some time the larva swims in the plankton, and then differentiates into a small worm.