308 CLASS V. CEPHALOPODA. 
the velamenta are expanded so as entirely to grasp each side of the shell, 
and when the animal is captured, they are suddenly retracted, in a state 
of alarm, and thrust down each side between the body and the shell 
so as to be plainly seen through it from the outside; the shell being 
thoroughly permeable to light, in its native condition, and not preventing 
the flesh of its inhabitant from assuming a certain degree of colour. We 
learn from the well-directed observations of Mr. Owen, that neither the 
membranous arms nor the shell are developed until some days after the 
Argonaut is excluded from the egg*, and this accounts for the compa- 
rative enormity of the nucleus. ‘‘ The young Cephalopod,” he observes, 
‘manifests a complete concordance between the form of its body and that 
of its shell, entirely filling the cavity ; and it has been noticed that at a 
certain age the animal begins to withdraw the extremity of the sack or 
abdominal portion of the body from the apex of the shell, to serve the 
purpose of oviposition, and this operation has been found to commence 
exactly and only when the ovarium begins to enlarge under the sexual 
stimulus.” . 
It may have been already noticed, from what has been said of the Ar- 
gonaut, that its entire history, both as regards the habits and organic 
structure of this animal, relates to the female. The fact is, that a male 
Argonaut does not yet appear to have been found, and it still becomes a 
question, as to whether the male produces a shell at allt. Several male 
Octopods have been discovered ; one variety indeed, says a correspondent 
of the Zoological Society, is very abundant in the Bay of Naples, and 
daily to be seen in the common market as an article of food: all of these, 
« 
* «Tn the ova most advanced, the distinction of head and body was established; the pig- 
ment of the eyes, the ink in the ink-bladder, the pigmental spots on the skin, were distinctly 
developed; the siphon, the beak, and the arms, were also discernible by a low microscopic 
power; the arms were short and simple; but the secreting membranes of the shell were not 
developed, and of the shell itself there was no trace. In the second memoir published by Ma- 
dame Power (1838), it is stated that the young Argonaut is extluded from the egg, as such, 
but naked, twenty-five days after oviposition, and that in ten or twelve days more, she disco- 
vered that they had formed their little shell.’—OweEn on the Argonaut. 
+ An Argonaut once discovered by Rafinesque without its shell, was immediately described 
by that author under the new generic title of Ocythée. 
