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"Foot of the seal, which opens and closes in the act of natation, the organ being folded upon itself during the non-effective or return stroke, and expanded during the effective or forward stroke. Due advantage is taken of this arrangement by the seal when swimming, the animal rotating on its long axis, so as to present the lower portion of the body and the feet obliquely to the water during the return stroke, and the flat, or the greatest available surface of both, during the effective or forward stroke."—Pettigrew, 1874

Foot of Seal

"Foot of the seal, which opens and closes in the act of natation, the organ being folded upon itself…

"Swan, in the act of swimming, the right foot being fully expanded and about to give the effective stroke, which is delivered outwards, downwards and backwards, as represented at r of fig. 50; the left foot being closed, and about to make the return stroke, as shown at s of fig. 50. In rapid swimming, the swan flexes its legs simultaneously and somewhat slowly; it then vigorously extends them."—Pettigrew, 1874

Swimming Swan

"Swan, in the act of swimming, the right foot being fully expanded and about to give the effective stroke,…