Male reproductive system of earthworm:

Testis : There are two pairs of testis one on eachside of the body in 10th and 11th segments. They produce sperm mother cells.
Seminal Vesicles : The sperm mother cells enter into the seminal vesicles present in the 9th and 12th segments. These cells mature into sperms in these seminal vesicles.
Vas deferens : Vas deferens are tube like strutures which arise from 10th and 11th segments by the funnels called spermidual funnels. By the cilliary action of the cilia in the spermidual funnels the sperms enter into the ducts - vas deferens. This duct sent out the matured sperms through an aperature called malegential aperture.
Prostate gland : This gland givesout its secretion which binds the sperms and this comes out through the male genital aperture.
Spermathecae : Spermathecae are sac like structures present in the 7, 8 and 9^th segments. There are 3 pairs and are helpful in the storing of the sperms of another earthworm.