158 OUTLINES OF EVOLUTIONARY BIOLOGY 



B. 



E. 



FIG. 15. Free-swimming Larvoe of Fandulue heteroditus. (From Stockard.) 



A. Normal larva, with anteriorly placed mouth (M). 



B. Incompletely cyclopean larva, with the two eyes joined and occupying the position 



usually taken by the mouth. 



C. Completely cyclopean larva, with single antero-median eye. Dorsal aspect. 



D. Lateral aspect of same, showing the ventral niouth (M). 



E. Ventral aspect of same; ys, yolk sac. 



