Figure 340 from Chapter 14 (Sperm Flagellum) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. Cross sections of sperm tails of a caddis fly illustrate differences between the organization of the insect sperm flagella and that of mammals, notably in the position of the nine outer elements in relation to the doublets of the axoneme. Image by David Phillips. A PDF copy of the accompanying chapter is available on the ASCB's BioEDUCATE website.