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 sliow 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 

 egg in the shell, and the little ones are 

 also hatched in this floating cradle. 

 Four or six species are at present known 

 — the species described by Aristotle and Phny, and the more ancient 

 naturalists — namely, A. argo, ov papyracea (Figs. 335 and 337), which 

 arc inhabitants of the Mediterranean as well as the Indian Ocean 

 and the Antilles. Two others, A. Oivcnii, belonging exclusively to 

 the Indian Ocean, and A. /lyans, which is met occasionally in the 

 Pacific and Atlantic Oceans. 



Fig. 338. 

 Argonauta papyracea in its shell. 



THE DISTRIBUTION OF THE MOLLUSCA. 



We have thought it better to treat this subject in a separate portion 

 af 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, 



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