. Evolution; its nature, its evidences, and its relation to religious thought . ce cither in theegg or else in very early embryonic states. The an-swer is found in the fact that this is the order of change * Proceedings of American Academy of Arts and Sciences, voLxiv, May, 1878. 174 EVIDENCES OF THE TRUTH OF EVOLUTION. in the phylogenic series. The earliest fish-tails wereeither like Fig. 61 or Fig. 60 ; never like Fig. 59. Theearliest of all were almost certainly like Fig. 61 ; thenthey became like Fig. 60 ; and, finally, only much later ingeological history (Jurassic or Cretaceous), they be
. Evolution; its nature, its evidences, and its relation to religious thought . ce cither in theegg or else in very early embryonic states. The an-swer is found in the fact that this is the order of change * Proceedings of American Academy of Arts and Sciences, voLxiv, May, 1878. 174 EVIDENCES OF THE TRUTH OF EVOLUTION. in the phylogenic series. The earliest fish-tails wereeither like Fig. 61 or Fig. 60 ; never like Fig. 59. Theearliest of all were almost certainly like Fig. 61 ; thenthey became like Fig. 60 ; and, finally, only much later ingeological history (Jurassic or Cretaceous), they becamelike Fig. 59. This order of change is still retained inthe embryonic development of the last introduced andmost specialized order of existing fishes. The family his-tory is repeated in the individual history. Similar changes have taken place in the form andstructure of birds tails. The earliest bird known—theJurassic Archaeopteryx — had a long reptilian tail oftwenty-one joints, each joint bearing a feather on eachside, right and left (Fig. 62). In the typical modern. Fig. 62.—Tail of the Archoeopteryx. bird, on the contrary, the tail-joints are diminished innumber, shortened up, and enlarged, and give out longfeathers, fan-like, to form the so-called tail (Fig. 63).The Archaeopteryx tail is vertebrated, the typical birdsnon-vertebrated. This shortening up of the tail did nottake place at once, but gradually. The Cretaceous birds,intermediate in time, had tails intermediate in struct-ure. The Hesperornis of Marsh had twelve joints. At PROOFS FROM KMBRYOLOGY. 175
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