Planarian undulipodia consisting of spermatazoa cell posterior protrusions. Planarian spermatozoa contain two flagella and are composed of 9 + 1 axonemal microtubule arrangements in their flagella (markedly different from the 9 + 2 structures generally observed in sperm of other animals). [ ]

Planarian undulipodia consisting of spermatazoa cell posterior protrusions. Planarian spermatozoa contain two flagella and are composed of 9 + 1 axonemal microtubule arrangements in their flagella (markedly different from the 9 + 2 structures generally observed in sperm of other animals). [ http://www.ncbi.nlm.nih.gov/pubmed/4190073 ]