. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . 176 EVOLUTION AND ANIMAL LIFE certain lizards, notably in a very primitive New Zealand lizardof the genus Sphenodon (Hatteria) (Fig. 109), andfcthat, in theselizards, the pineal body ends in a more or less perfect eye-likestructure placed between the true eyes in the center of theforehead. A trace of this eye is shown in the limbless lizardcalled slow worm (Anguis), of Europe, and in several Americanspecies. In the horned toad (Phrynosoma) (Fig. 110) its
. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . 176 EVOLUTION AND ANIMAL LIFE certain lizards, notably in a very primitive New Zealand lizardof the genus Sphenodon (Hatteria) (Fig. 109), andfcthat, in theselizards, the pineal body ends in a more or less perfect eye-likestructure placed between the true eyes in the center of theforehead. A trace of this eye is shown in the limbless lizardcalled slow worm (Anguis), of Europe, and in several Americanspecies. In the horned toad (Phrynosoma) (Fig. 110) its place ^^-^^^&m^^^- • v. •,.c-^.--- -:•-<:k• i^rt- .•l2?^ - -&-.». ^lfefie^yr »•. FIG. 110.—Head of lizard or horned toad, Phrynosom blainvillei, showing translucentpearly skin covering the pineal eye. (From specimen.) is covered by a translucent pearly scale. These lizards havein fact three eyes, and the pineal body is the nervous gang-lion from which the third eve arises. The natural conclusion V from this that all vertebrates originally had three eyes, is prob-ably a too-hasty one. Perhaps the pineal body was an organof sense, which developed into an eye in the lizards and theirancestors only, not in any of the Amphibians or fishes, and notin any mammals or birds, although these are descended fromreptilian stock. Whatever the origin or primitive function ofthe pineal ganglion, its existence in man as a vestigial organis due to the persistence of heredity. HEREDITY 177
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