Platyhelminthes, Aschelminthes, and Phoronida

Abstract

Arnold Lang (1884), an early authority of Platyhelminthes, especially of the turbellarians, was the first to apprehend clearly that the peculiar small white threads attached to bodies of Leptoplana and certain other Polycladida inhabiting the Gulf of Naples are not some kind of a mysterious parasite, but spermatophores in the form of thread-like packages of spermatozoa, wrapped in tough membranes. He also deserves the credit for pointing out that in Polycladida, the so-called male copulatory organ is not necessarily inserted into the female genital pore, but may serve the purpose of attaching the spermatophores to the surface of the partner’s body. The fixed spermatophore, having penetrated the skin and musculature, then releases the spermatozoa so as to enable them to invade the body.