No. 418.] NOTES ON LIVING NAUTILUS. 831 
the mantle; this then recedes, exposing the blackened portion 
of the shell. The eye is still seen peering over the notch at 
the lip of the shell. In this stage of retraction the animal will 
often remain for many minutes; if handled somewhat roughly 
it will retract still further, presenting a stage of closure shown 
in Fig. 8. Here the hood has closed over the aperture of the 
shell like a lid, or rather like an operculum; it has shrunken 
and flattened somewhat at the same time; behind it the : 
mantle has receded, leaving the. blackened area of the shell 
much in evidence. At the anterior end (Fig. 11) can still - 
be seen the turgid ends of some of the tentacles. The final 
closure of the aperture of the shell appears to take place by 
the bending down of the anterior flap-like portion of the hood, 
a process, however, which does not readily occur. Only by 
sharply stimulating this region have I seen total closure, and 
even then but for a few moments. If undisturbed, even if 
kept out of water, the animal slowly reopens. The hood first 
rises sluggishly, often separating itself behind from the shell, 
and the tentacles begin to protrude. More slowly does the 
mantle expand again over the blackened area. If still kept 
out of water the tentacles protrude and hang down over the 
edge of the shell in a flaccid mass. 
If an animal be taken out of water and held in an inverted 
position it will at first close just as has been described. After 
some time, hours (Professor Worcester tells me) in the case 
of specimens just out of water, minutes in the case of those 
Which have been kept in aquarium, the heavy fleshy “ head ” 
'of the animal will begin to droop downward, and will finally 
appear as shown in side view in Fig. 14 and in ventral view 
in Fig. rs. Whether under such circumstances the animal 
will ultimately fall out of its shell, I neglected to observe. 
I found, however, that by this means one can readily remove 
the animal from the shell and without breaking the delicate 
Siphuncular tube. The muscles attaching the body to the 
shell occupy very definite areas within the latero-dorsal region 
of the aperture and at the sides of the coil of the shell 2 and 
these areas are landmarked quite clearly in the inverted animal. 
The muscles may accordingly be separated from the shell, one s 
