Asexual and sexual germlines. (A) Animals capable of both sexual and asexual reproduction possess an asexual germline and a sexual germline. (B) Animals that reproduce exclusively asexually have nonetheless an asexual germline, which resides in the PriSCs. (C) Animals that exclusively reproduce sexually have lost the self-renewing capacities and/or somatic potential of their PriSCs and, therefore, only a classical sexual germline is present. PriSCs, primordial stem cells.