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Updated: June 22, 2025
We may say it has been bridged or filled with the humble ancestral forms that carried forward the precious evolutionary impulse of the vertebrate series till it culminated in man. All vestiges of that living bridge are now gone, and the legend of our crossing seems like a dream or a miracle.
Indeed the structure of an insect is entirely different from that of man or the quadrupeds, or any other vertebrate animal, and what we call head, thorax, abdomen, gills, stomach, skin, or lungs, or jaws, are called so simply for convenience, and not that they are made in the same way as those parts in the higher animals.
We may thus account even for the distinctness of whole classes from each other for instance, of birds from all other vertebrate animals by the belief that many ancient forms of life have been utterly lost, through which the early progenitors of birds were formerly connected with the early progenitors of the other vertebrate classes.
They may dry up or freeze or lie for a long time in the ground or water until the time comes when they are introduced into another host. The class Sporozoa is divided into five small groups or orders. These are dependent on two hosts for their existence, the sexual generation usually occuring in an insect or other invertebrate and the asexual generation in some vertebrate.
Still keeping to our comparison between the eye of vertebrates and that of molluscs, we may point out that the retina of the vertebrate is produced by an expansion in the rudimentary brain of the young embryo. It is a regular nervous centre which has moved toward the periphery.
So there must be A SPECIAL CREATION AT LAST. Hear him: "There appears, indeed, to be a limit given to the adaptability of every organism by the type of its tribe or phylum. Thus, for example, no vertebrate animal can acquire the ventral nerve chord of articulate animals instead of the characteristic spinal marrow of the vertebrate animals." History of Creation, vol. 1, p. 250.
In these important Vermalia the foremost section of the gut has already been converted into a gill-crate, and the vascular arches that rise in the wall of this from the ventral to the dorsal vessel have become branchial vessels. We have a further important advance in the Tunicates, which we have recognised as the nearest blood-relatives of our early vertebrate ancestors.
These are much more advanced and much younger than the lowest vertebrate, the Amphioxus, and the numerous skull-less vertebrates, related to the Amphioxus, that must have lived at that time. The whole of the invertebrate ancestors of the human race must have preceded these. The primordial age is followed by a much shorter division, the paleozoic or Primary age.
Weddahs. Australian negroes. Our task of detecting the extinct ancestors of our race among the vast numbers of animals known to us encounters very different difficulties in the various sections of man's stem-history. These were very great in the series of our invertebrate ancestors; they are much slighter in the subsequent series of our vertebrate ancestors.
A fortunate accident had directed the attention of this able observer almost simultaneously to the embryology of the lowest vertebrate, the Amphioxus, and that of an invertebrate, the close affinity of which to the Amphioxus had been least suspected, the Ascidia.
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