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Species of these genera occur in the Silurian, Devonian, and Carboniferous strata of Europe. Mr. Lonsdale remarks, that all these fossils have undoubtedly a Palaeozoic character, and that probably they correspond in age to a division of the system above the Silurian formations. The strata containing these remains are singular from the extreme variability of their mineralogical composition.
On the 20th of November, 1861, Major General Halleck issued the following Genera., Order which went even further, in that it expelled, as well as repelled Fugitive Slaves from our lines: "HEADQUARTERS DEPARTMENT OF MISSOURI, "St. Louis, November 20, 1861.
We may then reject Latreille's supposition, that the gossamer owes its origin indifferently to the young of several genera of spiders: although, as we have seen, the young of other spiders do possess the power of performing aerial voyages. Mr. During our different passages south of the Plata, I often towed astern a net made of bunting, and thus caught many curious animals.
And the reason is, that we can never determine what forms are specific without tracing them back to their origin, and this is impossible. Orders, genera, species, etc., are only so many lines of thought on which we arrange our classifications, just as the parallel wires of an abacus, with their sliding balls, are the lines on which we make our mathematical computations.
I have never had the least difficulty in accepting it; and all I have since found out of the relations of men with their fellow-creatures of other genera confirms me in the belief that the urgency is the paramount necessity.
Hitherto we have been dealing with those genera which have thick fleshy stems; but there still remain the genera Rhipsalis, Epiphyllum, and Phyllocactus, which are not capable of bearing the long period of drought advised for the former.
The other seven species of the old genera have all died out and have left no progeny. Or, which would probably be a far commoner case, two or three species of two or three alone of the six older genera will have been the parents of the six new genera; the other old species and the other whole genera having become utterly extinct.
The Fumariaceae include closely allied genera which are leaf-climbers and tendril-bearers. Lastly, a species of Bignonia is at the same time both a leaf-climber and a tendril-bearer; and other closely allied species are twiners. Tendrils of another kind consist of modified flower-peduncles. In this case we likewise have many interesting transitional states.
The West Indian Islands stand on a deeply submerged bank, nearly 1000 fathoms in depth, and here we find American forms, but the species and even the genera are distinct.
Now, if one thousand years may represent the period required for the evolution of the species S. nasalis, and of the other species of the genus Semnopithecus; ten times that period should, I think, be allowed for the differentiation of that genus, the African Cercopithecus and the other genera of the family Simiidæ the differences between the genera being certainly more than tenfold greater than those between the species of the same genus.
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