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Updated: May 11, 2025
Cut very carefully up under rim of horn bases when removing skin from around them, using care not to haggle edge of skin. Use same care in skinning out the face, splitting lips and eyelids and skinning out the ears as in small mammal specimen.
The mammals have their first coming of age when they are weaned; and it is noteworthy that this rather cruel and selfish operation on the part of the parent has to be performed resolutely, with claws and teeth; for your little mammal does not want to be weaned, and yields only to a pretty rough assertion of the right of the parent to be relieved of the child as soon as the child is old enough to bear the separation.
The epoch at which these important advances were made, and the foundation of the Mammal class was laid, may be put with great probability in the first section of the Mesozoic or secondary age the Triassic period. The oldest fossil remains of mammals that we know were found in strata that belong to the earliest Triassic period the upper Kueper.
From records here unearthed, the racial evolution of many mammals has in the past few years been made out in greater or less detail. A lemuroid form of mammal, believed to be of the type from which man has descended, has also been found in these beds.
But if the same species can be produced at two separate points, why do we not find a single mammal common to Europe and Australia or South America?
We cannot, for instance, suppose that in the embryos of the vertebrata the peculiar loop-like course of the arteries near the branchial slits are related to similar conditions, in the young mammal which is nourished in the womb of its mother, in the egg of the bird which is hatched in a nest, and in the spawn of a frog under water.
But the pectoral fin of a fish is equally 'adapted' for aquatic locomotion, but it is certainly not the fore-leg of a terrestrial mammal adapted for that purpose. The original meaning of adaptation in animals and plants, of organic adaptation to use another term, is the relation of a mechanism to its action or of a tool to its work.
The fish there diverges and passes along a line apart, and peculiar to A itself, to its mature state at F. The reptile, bird, and mammal, go on together to C, where the reptile diverges in like manner, and advances by itself to R. The bird diverges at D, and goes on to B. The mammal then goes forward in a straight line to the highest point of organization at M. This diagram shews only the main ramifications; but the reader must suppose minor ones, representing the subordinate differences of orders, tribes, families, genera, &c., if he wishes to extend his views to the whole varieties of being in the animal kingdom.
This is an actual remnant, a reminder of the past, when the eggs of the mammals were also packed with yolk and the growing embryo secured its nourishment exactly as does the maturing chick. But a new method has been provided for the mammal, and consequently the yolksac, though it has not entirely disappeared, has no nutritive content for the growth of the embryo.
The outlying remainder of the first gill-cleft is the rudiment of the external meatus. From its inner part we get the tympanic cavity, and, further inward still, the Eustachian tube. Connected with this is the development of the three bones of the mammal ear from the first two gill-arches; the hammer and anvil are formed from the first, the stirrup from the upper end of the second, gill-arch.
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