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The same with the skeletons in the invertebrates, from membrane to cartilage, from cartilage to bone, so that the primitive cartilage remaining in any part of the skeleton is considered a mark of inferiority. According to Cope, there has been progressive improvement in the mechanism of the body it has become a better and better machine.
He was working at philosophy and getting up before the sun to make experiments on the susceptibility to light of the invertebrates; by way of studying English and politics at the same time, he was translating Mr.
Those long ages of unicellular life in the old seas, how immense they appear to have been; then how the age of invertebrates dragged on, millions upon millions of years; then the age of fishes; the Palaeozoic age, how vast put by Haeckel at thirty-four millions of years, adding rock strata forty-one thousand feet thick; then the Mesozoic or third period, the age of reptiles, eleven million years, with strata twelve thousand feet thick.
The eye of the Pecten presents a retina, a cornea, a lens of cellular structure like our own. There is even that peculiar inversion of retinal elements which is not met with, in general, in the retina of the invertebrates.
In most cases, the cells are connected in chains, and we begin to see the vague outline of the larger plant. When we had reached this stage in the development of animal life, we found great difficulty in imagining how the chief lines of the higher Invertebrates took their rise from the Archaean chaos of early many-celled forms.
We cannot say that the vertebrates are descended from the Ascidiae and still less the reverse but we can say that of all the invertebrates it is the Tunicates, and, within this group, the Ascidiae, that are the nearest blood-relatives of the ancient stem-form of the vertebrates.
Thus it was that Cuvier came forward with a brand-new classification of the animal kingdom, establishing four great types of being, which he called vertebrates, mollusks, articulates, and radiates. Lamarck had shortly before established the broad distinction between animals with and those without a backbone; Cuvier's Classification divided the latter the invertebrates into three minor groups.
They used to try 'em all, big and little, wild and domesticated, mammals and invertebrates." "Oh, come!" exclaimed Tutt. "I may not know much law, but " "Between 1120 and 1740 they prosecuted in France alone no less than ninety-two animals. The last one was a cow." "A cow hasn't much intelligence," observed Tutt. "And they tried fleas," added Mr. Tutt.
For in the zoölogical system also these main-types of the invertebrates do not stand one above the other, but by the side of each other: at most, the radiata, the worms, the mollusca, and the articulata, take their places above the zoöphytes. Only within the main-types, in the classes, orders, etc., do differences in rank take effect; and even here, not without exception.
Backbones are called by the Wise Men vertebrae; animals that have backbones are named Vertebrates; and animals that lack backbones are named Invertebrates." "Tell us the names of some Invertebrates, please, Doctor," said Rap. "Well, all sorts of insects are Invertebrates, and so are lobsters and crabs, oysters and clams, worms, starfishes, jelly-fishes, corals, and even sponges.
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