SECTION III.
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 further, 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 (Pulmonariæ) are Spiders and Scorpions; and we have evidence to show that fossil remains of both these families exist in strata of very high antiquity.
