Fig. 1.

(A) Mating slender crabs Metacarcinus gracilis in precopulatory embrace, an example of contact-mating animals. Image courtesy of Ken Kurtis. (B) Broadcast-spawning flower coral Eusmilia fastigiata . Image courtesy of Ned DeLoach. (C) Diversity curve of marine animals since the Ordovician Period, categorized according to fertilization mode. Units of geological time (MA) means millions of years ago. Data taken from Bush et al. (1); see Bush et al. for details on data standardization methods.