AbstractTwinning or duplication was observed in 28 eggs of the common snapping turtle,Chelydra serpentina serpentina.The methods of observation made detection of separate blastodiscs relatively certain, that of duplication within a blastodisc less so. Only two of the latter were found. Twins occurred in about 1% of the eggs; 26% of the clutches had one or more abnormal eggs. Twinned blastodiscs developed normally in early stages. When incubated through hatching, 12 out of 12 sets of twins developed unequally so that one was essentially normal, the other was small and not viable. In one case, in which the carapace of the smaller twin was three quarters the length of the larger, both died during hatching. The pigmentation patterns of the carapace of these twins differed; this indicates that they are fraternal rather than identical twins.
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