title: Spermiogenesis in the sea urchins Arbacia lixula and Echinometra locunter (Echinodermata).
mesh_terms: D000818:Animals; D008297:Male; D012617:Sea Urchins / Q000166:cytology*; D013045:Species Specificity; D013087:Spermatids / Q000648:ultrastructure; D013091:Spermatogenesis; D013094:Spermatozoa / Q000648:ultrastructure