The evolution of the earth and its inhabitants; a series delivered before the Yale chapter of the Sigma xi during the academic year 1916-1917 . ig. 16.) That this locomotivedevice might have been developed in static waters is not denied,for some marine worm-like organisms swim by a wrigglingmovement, though invariably in the dorso-ventral plane, butthere is in the sea little incentive to enforce its rapid perfec-tion, such as dynamic waters would produce. Hence theassumption that the vertebrates are the outcome of terrestrialwaters. To illustrate the means whereby the evolution wasinitiated, C
The evolution of the earth and its inhabitants; a series delivered before the Yale chapter of the Sigma xi during the academic year 1916-1917 . ig. 16.) That this locomotivedevice might have been developed in static waters is not denied,for some marine worm-like organisms swim by a wrigglingmovement, though invariably in the dorso-ventral plane, butthere is in the sea little incentive to enforce its rapid perfec-tion, such as dynamic waters would produce. Hence theassumption that the vertebrates are the outcome of terrestrialwaters. To illustrate the means whereby the evolution wasinitiated, Chamberlin1 has discussed the peculiar habit of astream-borne lamprey, Petromyzon (Fig. 16, E, left-hand eel),which adheres to the bottom by its suctorial mouth and allowsits body to undulate in the pulsating current as a flag iswhipped in the breeze or a rope of grass in the stream. Unlessthe stream be very shallow so as to cause distinct vertical dis-placements of the water, this undulation is always lateral or 1 Chamberlin, T. C., On the Habitat of the Early Vertebrates. , vol. 8, 1900, pp. 400-412. B sp^- A n -1* U -q^C^-^. COMPRESSED E
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