. Evolution; its nature, its evidences, and its relation to religious thought . Jig. 60.—Heterocercal or vertebratcd tail-tin. a, form ; b, structure. PROOFS FROM EMBRYOLOGY. < 6 (Fig. 59, b) ; in (ho latter the backbone runs throughthe tin to its very point, growing slenderer by decrees,ami giving oil raya above and below from each joint,hut the rays on the lower side are much longer (Fig. GO,b). This style of tin is therefore, vertebrated, the othernon-vertebrated. Figs. 59 and ho show these two stylesin form and structure. Hut there is still another stylofound only in the lowesl and most
. Evolution; its nature, its evidences, and its relation to religious thought . Jig. 60.—Heterocercal or vertebratcd tail-tin. a, form ; b, structure. PROOFS FROM EMBRYOLOGY. < 6 (Fig. 59, b) ; in (ho latter the backbone runs throughthe tin to its very point, growing slenderer by decrees,ami giving oil raya above and below from each joint,hut the rays on the lower side are much longer (Fig. GO,b). This style of tin is therefore, vertebrated, the othernon-vertebrated. Figs. 59 and ho show these two stylesin form and structure. Hut there is still another stylofound only in the lowesl and most generalized forms offishes. In these the tail-fin is vertebrated and yet sym-metrical This style is shown in Fig. 61, \ and Fig. 01.—Vertebrated but symmetrical fin. a, form ; n, structure. Now, in the development of a teleost fish (Fig. 58),as has heon shown by Alexander Agassiz,* the tail-fin isfirst like Fig. 01 ; then becomes heterocercal, like Fig. 60;and, finally, becomes homocercal like Fig. 59. Why so?Not because there is any special advantage in this succes-sion of forms ; for the changes take place 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 th
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectreligion, bookyear189
