498 THE OCEAN WORLD. 
turned, and the animal is nearly invisible. If frightened, it entirely 
submerges itself, and sinks to the bottom. 
These little beings share with other Cephalopods the strange 
Fig 337.—Argonauta papyracea, as it swims by means f its locomotive tube. 
faculty of changing colour under the influence of some vivid impres- 
sion ; but their graceful and delicate organisation redeems them from 
the charge we have brought against the cuttles. The Argonaut can 
blush, turn pale, and show through its transparent shell its body 
changing in sudden shades; but it 
never exhibits those bristling, unplea- 
sant tubercles, the inheritance of the 
larger and coarser Cephalopods—the 
tyrants of the sea. 
The male Argonauts are very small, 
often not a tenth part of the size of 
the females, which alone possess the 
shells. 
The female Argonaut carries its 
Fig. 338. egg in the shell, and the little ones are 
Argonauta papyracea ints shell. 159 hatched in this floating cradle. 
Four or six species are at present known 
—the species described by Aristotle and Pliny, and the more ancient 
naturalists—namely, A. argo, or papyracea (Figs. 335 and 337), which 
are inhabitants of the Mediterranean as well as the Indian Ocean 
and the Antilles. Two others, 4. Owendt, belonging exclusively to 
the Indian Ocean, and A. Ayans, which is met occasionally in the 
Pacific and Atlantic Oceans. 
THE DISTRIBUTION OF THE MOLLUSCA. 
We have thought it better to treat this subject in a separate portion 
of this chapter, for its vast and complicated nature renders it other- 
wise difficult to handle, except in a space which would exceed the 
limits of this work, 
