Fig. 198, A-F. — Animal spermatozoa. A, Plagiostomum, a turbellarian (from Bohmig, 

 1891); B, Castroda and C, Mesostomum, both turbellaria (from Luther, 1904); D, Ascaris 

 megalocephala, a nematode (from Scheben, 1905); E, Nereis, a polychete annelid (from F. R. 

 Lillie, 1912); F, Paliidina, a gasteropod (from Meves, 1903). 



