When we hear of fishes wandering about on the dry land, we cannot wonder that some insects and arachnidans should depart so strangely from the usual habits of their class as to select the sea for their habitation.
"There is a minute marine spider," says Mr. Gosse, "very common on most parts of the coast, crawling sluggishly upon the smaller sea-weeds, which seems, from its lack of centralisation, to realise our infant ideas of Mr. Nobody; but zoologists have designated him as Nymphon gracile. Widely different from the spiders of terra firma, in which an abdomen some ten times as bulky as all the rest of the animal put together is the most characteristic feature, the belly of our marine friend is reduced to an atom not so big as a single joint of one of his eight legs; though his thorax is more considerable, this is little more than the extended line formed by the successive points of union of the said legs. These latter, on the other hand, are long, stout, well-armed, and many-jointed; but, apparently from the lack of the centralising principle, they are moved heavily, sprawled hither and thither, and dragged about like the limbs of an unfortunate who is afflicted with the gout." This strange little creature has four eyes gleaming like diamonds, respires by the skin, and its stomach is prolonged into each of its eight legs, which are thus made the seats of digestion. Mr. Nobody and his marine relations, some of which also attach themselves to fishes, form the small group of the Pycnogonida (πυκνος, frequent; γὁνυ knee) thus named from their many-jointed legs.
It is a well-known fact that the winds will sometimes waft butterflies to an immense distance from the shore. Thus Acherontia atropos has been found on the Atlantic a thousand miles from the nearest land; and while Mr. Darwin was in the bay of San Blas, in Patagonia, he saw thousands of butterflies hovering over the sea as far as the eye could reach. These insects, of course, are nothing but stray wanderers on an alien and hostile element; but Leptopus longipes, a species of bug, makes the salt water its home; the Halobates, another hemipterous insect, faces the tranquil mirror of the tropical seas as leisurely as our water-bugs sport on the glassy surface of our ponds, and the Gyrinus marinus, a beetle belonging to the family of the whirligigs, ambitiously seeks a wide expanse, and may be seen curvetting about on the surface of the sea, and darting down every now and then to seize its prey.
Stenopus hispidus.
[CHAP. XIV.]
MARINE ANNELIDES.
The Annelides in general.—The Eunice sanguinea.—Beauty of the Marine Annelides.—The Giant Nemertes.—The Food and Enemies of the Annelides.—The Tubicole Annelides.—The Rotifera—Their Wonderful Organisation.—The Synchæta Baltica.