Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 11, 2025
When we reflect on these facts, here given much too briefly, with respect to the wide, diversified, and graduated range of structure in the eyes of the lower animals; and when we bear in mind how small the number of all living forms must be in comparison with those which have become extinct, the difficulty ceases to be very great in believing that natural selection may have converted the simple apparatus of an optic nerve, coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the Articulata class.
In the great class of the Articulata, we may start from an optic nerve simply coated with pigment, the latter sometimes forming a sort of pupil, but destitute of lens or other optical contrivance. With insects it is now known that the numerous facets on the cornea of their great compound eyes form true lenses, and that the cones include curiously modified nervous filaments.
But these organs in the Articulata are so much diversified that Muller formerly made three main classes with seven subdivisions, besides a fourth main class of aggregated simple eyes.
There are crustaceans at the opposite ends of the series, which have hardly a character in common; yet the species at both ends, from being plainly allied to others, and these to others, and so onwards, can be recognised as unequivocally belonging to this, and to no other class of the Articulata.
But in the higher Annulosa, called Articulata, sundry of the anterior pairs of ganglia, besides growing larger, unite in one mass; and this great cephalic ganglion having become the co-ordinator of all the creature's movements, there no longer exists much local independence. Now may we not in the growth of a consolidated kingdom out of petty sovereignties or baronies, observe analogous changes?
It must suffice for our purpose to bear in mind that an indefinite repetition of the same part or organ is the common characteristic, as Owen has remarked, of all low or little specialised forms; therefore the unknown progenitor of the Vertebrata probably possessed many vertebrae; the unknown progenitor of the Articulata, many segments; and the unknown progenitor of flowering plants, many leaves arranged in one or more spires.
"Vertebra, articulata, mollusca, and radiata are evolved by mortal and material thought." "Theorizing about man's development from mushrooms to monkeys, and from monkeys into men, amounts to nothing in the right direction, and very much in the wrong." But it is not only with the natural sciences that Mrs. Eddy is displeased.
But the Crustacea exhibit many peculiar features in common with insects, spiders, and centipedes, so that these are grouped into the still larger assemblage or "province" Articulata; and, finally, the relations which these have to worms and other lower animals, are expressed by combining the whole vast aggregate into the sub-kingdom of Annulosa.
If, then, we attempt to map out the Articulata, we must, I think, regard the Crustacea and Insecta as continents, the Myriopoda and Collembola as islands of less importance, but still detached.
These four great branches of the animal world are the vertebrata, mollusca, articulata, and radiata. Comparative anatomy found in Cuvier a student who appreciated its importance and revived its efficiency and honors.
Word Of The Day
Others Looking