THE ARGONAUT. PAPER NAUTILUS - FAMILY ARGONAUTIDIE. Genus ARGONAUTA, Linn.
Habitat.—Tropical and warm seas.
The two cephalopod mollusks with external shells were ob served centuries ago sailing about in their graceful boats, and each was called Nautilus, which means "little sailor." One has a pearly shell; the other a white one, thin as paper. So one was called the Pearly Nautilus, the other the Paper Nautilus.
The pearly one was rarely seen. But as summer came on, fleets of the paper nautili appeared off the Mediterranean coasts. Writers of Greece and Rome called them Argonauta, an allusion to the fabled Argonauts, who, under Jason, sailed away to find the Golden Fleece.
Now, is n't it strange that a large and conspicuous mollusk like Argonauta, sailing all warm seas, appearing by hundreds close to shore where men could pick it up and make its acquain tance, should have kept the secrets of its ways of life so long 441 The Argonaut. Paper Nautilus from inquisitive mankind? As late as I850 little more was known about it than Aristotle wrote four centuries before Christ. The ancients noticed that the shell has no muscular attach ment to the body. The mollusk relaxes its hold when handled and the shell slips away. Wise people said: "Here we have a parasite like the hermit crab, that has picked up a shell and moved into it." But nobody could clear up the mystery of the shell. Where and what was the mollusk to which it rightfully and originally belonged? Nobody could say with certainty.
Nor could anybody say whether the ship-wrecked Argonaut could live without the shell. Nobody ever saw a male Argo nauta. The specimens seen were all females.
About the middle of the nineteenth century scientific interest in the paper nautilus reached white heat. Two of the leading zoologists of the time tried to convince all the rest that the argonaut has no means of secreting a shell. They believed the shell to be that of a large sea snail. The arguments upholding these theories were very clever, but facts were lacking.
Another mystery appeared for solution. A long, wriggling, whip-like object was found hiding in the folds of the mantle. It looked like the arm of an octopus, and was full of spermatozoa. Some authors believed it to be a parasite; others jumped joyfully at the conclusion that at last they had found the male argonaut.
While these men argued, a lady at Messina, Italy, was closing a long series of observations on the development of Argonauta. It is not difficult to keep the eggs in a marine aquarium and to watch the young ones grow up. Madame Jeannette Power saw the eggs hatch perfectly formed and very active young, which exhibited no sign of a shell. In ten or twelve days the shell was observed to be forming in some individuals.
This shell is a strange and unusual one. It is not truly a shell at all, but a cradle secreted to protect the eggs in the breed ing season. The male has no shell. The shell glands of mollusks are in the mantle edge. Here is a unique exception. The two dorsal arms spread out into large webs at their extremities. These two thin "vela" have the shell glands; the mantle has none. When the young female is one inch long it begins to form a shell. The body rests in the mouth of the shell, though it ex tends pretty far out of it, and the two inflated web-like arms always clasp the two sides of the shell tightly, and deposits of 442 The Argonaut. Paper Nautilus shelly substance are constantly added. Serious breaks in the delicate porcelain shell are repaired by this web; the strangest recorded incident is of the cementing in of a broken piece, but wrong side out.