FIGURE 4 in New species of the earthworm genus Zapatadrilus (Clitellata, Acanthodrilidae) from northern Mexico

FIGURE 4. Right prostate glands of segment 18 of the three new species. A–C. External appearance, dorsal view, photograph. D–G. Cross section, scanning electron micrographs. A,D. Zapatadrilus aurelius sp. nov. B,E. Zapatadrilus montezumensis sp. nov. C,F,G. Zapatadrilus huastecus sp. nov. In external appearance (A–C), the prostates of the three species are racemose, but internally (D–G), the cross sections reveal the presence of a single central duct; therefore the prostates are tubulo-racemose. The central duct is indicated by a red arrow. Scale bars = 100µm (D,E), 50µm (F), 10µm (G).