PROFICIENT YEARS AT SPORTS state, regional, national, and world championships.* With the foregoing data numerous age curves were constructed but in this brief article it will be possible to present only a summary of the findings. In Figure 10 the solid line presents the combined data for the 630 rifle and pistol championships. When the data for the rifle and for the pistol shooters were plotted separately, the peaks of both of the age curves were found to occur at ages 25 to 29 inclusive. Biological fecundity — —— — Marksmanship TOG et Individwl ——— 2 1 1 1 15 20 25 30 3 40 45 50 55 60 65 Ficure 9. Chronological ages at which Ficure 10. A, chronological ages at American Bowling Congress Champion- ships were won or retained. A, team performance; B, individual performance. which 630 rifle and pistol champion- ships were won; B, ages of fathers of children born in the United States in the year 1931. The dash line in Figure 10 presents information regarding biological fecundity. This dash line, which reveals the number of men who become fathers at successive age levels, is based upon more than 2,000,000 births which occurred during the year 1931.’ Since similar age curves were found when data for fecundity were plotted separately for several different years, it seems safe to assume that the dash line in Figure 10 is a trustworthy portrayal of the facts regarding man’s biological fecundity at various age levels. It will be noted that there is much similarity between the two curves of Figure 1o.f It is because of this marked similarity that these two age curves are superimposed in Figure 10. DUCK PIN BOWLERS Figure 11 presents data for Duck Pin Bowlers.t In this figure the solid line presents data for men only, e.g., for 91 National Duck Pin * Data regarding the rifle and pistol shooters were supplied by Col. M. A. Reckord. Thanks are expressed herewith for this wholehearted cooperation. + In Figure ro neither of the age curves makes any allowance for the fact that there are more young men than older men. When such allowance is made, however, the two age curves exhibit about the same degree of similarity. t For the data regarding the Duck Pin Bowling champions, the writer is indebted to Mr. G. L. Isemann, Secretary of the National Duck Pin Bowling Congress.