Abstract
Alpha-estradiol benzoate induced the dissolution of 1 or 2 anterior hemai spines in a significant number of immature and maturing male platyfish but elicited no response in adult males. Methyl testosterone, administered to adult females, induced the fusion of 2 series of small, basal bony elements, the mesonosts and baseosts. The mesonosts, ordinarily discrete, became fused to the ventral surfaces of the interhemal spines. The baseosts, normally bipartite, became unipartite.