. Evolution and its relation to religious thought . o rep-tiles. Thus, again, the phylogeuy, the taxonomy, andthe ontogeny, are in complete accord. But the argument for eyolution does not stop birds and mammals have come from reptiles, andtherefore from fishes, we may expect to find some evi-dences of the same kind still lingering in the great arter-ies. And such we do find. It is a most curious andsignificant fact that, in the early embryonic condition ofbirds and mammals, including man himself, we findon each side of the neck several gill-slits, each with itsgill-arch, and therefore
. Evolution and its relation to religious thought . o rep-tiles. Thus, again, the phylogeuy, the taxonomy, andthe ontogeny, are in complete accord. But the argument for eyolution does not stop birds and mammals have come from reptiles, andtherefore from fishes, we may expect to find some evi-dences of the same kind still lingering in the great arter-ies. And such we do find. It is a most curious andsignificant fact that, in the early embryonic condition ofbirds and mammals, including man himself, we findon each side of the neck several gill-slits, each with itsgill-arch, and therefore several aortic arches on eachside, precisely similar to what we have already arches are subsequently, some of them, obliterated ;some modified to form the one aortic arch, and someof them still more modified to form the other great arter-ies coming from the heart to supply the head and fore-limbs. PROOFS FROM EMBRYOLOGY. 139 This is so beautiful and convincing an example, andone so generally unfamiliar, to even intelligent Fig. 40.—Diagram of mammalian heart, a, aorta ; p, pulmonary artery;scsc\ subclavium on each side; €c\ carotids on each side. not especially acquainted with biology, that it is best toexplain it more fully. In Fig. 40 we give a mammalianheart and outgoing vessels, very slightly modified, so asto suggest the process of change. In Fig. 41 we givean ideal diagram representing the primitive aortic archesas they exist in the embryo of mammals, birds, andreptiles. It represents, also, substantially, the arches asthey exist in the mature condition in the most reptilianfishes (dipnoi) and in some sharks, except that in these 140 EVIDENCES OF THE TPwUTH OF EVOLUTIOIsr. the arches are of course furnished with gill-fringes. Wewill use this figure, therefore, to rej)resent both the em-
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