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The results arising from these facts are not confined to animal Physiology; they give information also regarding the condition of the ancient Sea and ancient Atmosphere, and the relations of both these media to Light, at that remote period when the earliest marine animals were furnished with instruments of vision, in which the minute optical adaptations were the same that impart the perception of light to Crustaceans now living at the bottom of the sea.

With respect to the waters wherein the Trilobites maintained their existence throughout the entire period of the Transition formation, we conclude that they could not have been that imaginary turbid and compound Chaotic fluid, from the precipitates of which some Geologists have subposed the materials of the surface of the earth to be derived; because the structure of the eyes of these animals is such, that any kind of fluid in which they could have been efficient at the bottom, must have been pure and transparent enough to allow the passage of light to organs of vision, the nature of which is so fully disclosed by the state of perfection in which they are preserved.

With regard to the Atmosphere also we infer, that had it differed materially from its actual condition, it might have so far affected the rays of Light, that a corresponding difference from the eyes of existing Crustaceans would have been found in the organs on which the impressions of such rays were then received.

Regarding Light itself also, we learn from the resemblance of these most ancient organizations to existing eyes, that the mutual relations of Light to the Eye, and of the Eye to Light, were the same at the time when Crustaceans endowed with the faculty of vision were first placed at the bottom of the primeval seas, as at the present moment.

Thus we firtl among the earliest organic remains, an Optical instrument of most curious construction, adapted to produce vision of a peculiar kind, in the then existing representatives of one great Class in the Articulated division of the Animal Kingdom. We do not find this instrument passing onwards, as it were, through a series of experimental changes, from more simple into more complex forms; it was created at the very first, in the fulness of perfect adaptation to the uses and condition of the class of creatures, to which this kind of eye has ever been, and is still appropriate.

If we should discover a microscope, or telescope, in the hand of an Egyptian Mummy, or beneath the ruins of Herculaneum, it would be impossible to deny that a knowledge of the principles of Optics existed in the mind by which sucli an instrument had been contrived. The same inference follows, but with cumulative force, when we see nearly four hundred microscopic lenses set side by side, in the compound eye of a fossil Trilobite; and the weight of the argument is multiplied a thousand fold, when we look to the infinite variety of adaptations by which similar instruments have been modified, through endless genera and species, from the long-lost Trilobites, of the Transition strata, through the extinct Crustaceans of the Secondary and Tertiary formations, and thence onward throughout existing Crustaceans, and the countless hosts of living Insects.

It appears impossible to resist the conclusions as to Unity of Design in a common Author, which are thus attested by such cumulative evidences of Creative Intelligence and Power; both, as infinitely surpassing the most exalted faculties of the human mind, as the mechanisms of the natural world, when magnified by the highest microscopes, are found to transcend the most perfect productions of human art.

SECTION HI.

Third Class of Articulated Animals.

FOSSIL ARACHNIDANS.

Under the relations that now subsist between the animal and vegetable kingdoms, the connexion of terrestrial Plants with Insects is so direct and universal, that each species of plant is considered to afford nutriment to three or four species of insects. The General principle which we have traced throughout the Secondary and Tertiary formations. ever operating to maintain on the surface of the earth the greatest possible amount of life, affords a strong antecedent probability that so large a mass of terrestrial vegetables as that which is preserved in the Carboniferous strata of the Transition series, held the same relation, as the basis of nutriment to Insect families of this early date, that modern vegetables do to this most numerous class of existing terrestrial animals.

Still farther, the actual provisions for restraining this Insect class within due bounds, by the controlling agency of the carnivorous Arachnidans would lead us to expect that Spiders and Scorpions were employed in similar service during the successive geological epochs, in which we have evidence of the abundant growth of terrestrial vegetables.

Some recent discoveries confirm the argument from these analogies, by the test of actual observation. The two great families in the higher order of living Arachnidans (Pulmonariae) are Spiders and Scorpions; and we have evidence to show that fossil remains of both these families exist in. strata of very high antiquity.

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Fossil Spiders.

Although no Spiders have been yet discovered in any rocks so ancient as the Carboniferous series, the presence of Insects in this series, and also of Scorpions, renders it highly probable that the cognate family of Spiders was coordinate with Scorpions, in restraining the Insect tribes of this early epoch, and that it will ere long be recognised among its fossil remains.*

The existence of Spiders in the Jurassic portion of the Secondary formations has been established, by Count Munter's discovery of two species in the lithographic limestone of Solenhofen. M. Marcel de Serres and Mr. Murchison have discovered fossil Spiders in Fresh-water Tertiary strata near Aix in Provence. (See PI . 46", Fig. 12.)

* The animal found by Mr. W. Anslice in the Iron-stone of Coalbrook Dale, and noticed by Mr. Prestwich as "apparently a Spider" (Phil. Mag. May, 1834, v. iv. p.. 376,) has been subsequently laid open by me, and shown to be an Insect, belonging to the family of Ciirculionidse. (PI 46", Fig. 1.) At the. time when it was figured, and supposed to be a Spider, its head and tail were covered by iron-stone, and its appearance much resembled an animal of this kind. Mr. I'restwich announces also the discovery, in the same formation, of a Coleopterous Insect, which will be farther described in our next section, as referable also to the Circu. lion ids.

It is scarcely possible to ascertain the precise nature of the animals, rudely figured as Spiders and Insects on Coal slate by Lhwyd, (Ichnograph, Tab 4,) and copied by Parkinson, (Org. Rem. V. iii. PI. 17, Figs. 3, 4, 5, 6;) but his opinion of them is rendered highly probable by the recent discoveries in Coalbrook Dale: "Scripsi olim suepicari me Araueorum quorundam icones, uni cum Lithophytis in Sohislo Carbonaria observasse: hoc jam ulteriore experientia. edoctus aperte assero. Alias ieones habeo, qua? ad Scarabeeorum genus quam proxime accedunt. In posterum ergo non tantum Lthophyta, sed etqusedam Insecta in hoc lapidc investigarc conabimur."' Lhwyd Epist. iii, ad fin.

Fossil Scorpions.

The address of my friend Count Sternberg to the members of the National Museum of Bohemia (Prague, 1835,) contains an account of his discovery of a fossil Scorpion in the ancient Coal formation at the village of Chomle, near Radnitz, on the S. W. of Prague. This most instructive fossil (the first of its kind yet noticed) -was found in July,. 1834, in a stone-quarry, on the outcrop of the Coal measures,, near a spot where coal has been wrought since the sixteenth century. In the same quarry were found four erect trunks of trees, and numerous vegetable remains,- of the same species that occur in the great Coal formation of England.

A series of drawing? of this Scorpion was submitted to a select committee at the meeting of Naturalists and Physicians of Germany, in, Stutgard, 1834; and from their report the subjoined particulars are taken. All our Figures,. (PI. 45'.) are copied from, those attached to this Report, in the Transactions of the Museum of Bohemia,. April,. 1835.*

* This fossil Scorpion- differs from existing specie;:, less in general structure than in the position of the eyes. In the latter respect, it approaches nearest to the genus Androctonus, which, like it, has twelve eyes, but differently disposed from those of the fossil species. From the nearly circular arrangement of these organs in the latter animal, it has been ranged under a new genus, Cyclopthalmus.

The sockets of all these twelve ayes are perfectly preserved, (PI. 46'. fig. 3.) One of the small eyes, and the left large eye, still retain their form, with the cornea preserved in a wrinkled state, and their interior filled with earth,

The jaws also are very distinct, but in a reversed position.. (Fl. 46'. fig.. 2. a.) Both these jaws have three projecting teeth, and one of them (PI. 46', Figs. 4. S.) exhibits, when magnified, the hairs with which its horny integument was covered.

The rings of the thorax, (apparently eight) and of the tail, are too much dislocated' for their number to be accurately distinguished, but they differ from all known species. The view of the back (PI. 46', Fig. 1.) has been obtained by cutting into the stone from behind.

The under surface of the animal is well exposed in Fig..2, with its cha

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