Lign. 11:—Xanthidium palmatum in flint: highly magnified.
But what are these bodies?—They are the durable cases of animalcules, many species of which swarm in our seas, and are so minute, that thousands may be contained in a drop of water! In a living state, the case is flexible and filled with a granular jelly, which is the soft body of the animalcule, and the tubes and the outer surface are invested with a similar substance. After death the soft parts dissolve; but the case and its spines often remain unchanged.
In another magnified portion of the pebble, a specimen of the microscopic discoidal shells which we have already seen compose the greater part of the white chalk ([Lign. 5], p. 14), is beautifully displayed when viewed by transmitted light, under a highly magnifying power ([Lign. 12]).[K] Our investigation has thus shown, that a great part of the pebble is actually composed of the aggregated fossil remains of animalcules, so minute as to elude our unassisted vision, but which the magic power of the microscope reveals to us, preserved, like flies in amber, in all their original sharpness of outline and delicacy of structure.
[K] [Note VI.] Rotaliæ in chalk and flint.
ROTALIA IN FLINT.
Lign. 12:—Rotalia in flint: highly magnified.
On another fragment of this stone two glittering specks, not larger than a pin's head, are discernible ([Lign. 9]): these with a magnifier of moderate power, are seen at a glance to be scales of fishes. But they differ from each other; both have the surface smooth, and without enamel: in the one the margin or edge is simple ([fig. 3]); in the other, it is divided like the teeth of a comb ([fig. 2]);—trifling as this difference may appear, it is sufficient to enable the naturalist to determine that the fishes which furnished these scales belonged to two distinct orders, of which the Salmon and the Mullet are living examples.